chemistry xii 1-5 inorganic

Professor Jee Collegiate Chemistry XII

CHAPTER # 01PERIODIC CLASSIFICATION

DOBEREINER’S CLASSIFICATION:

German chemist Johan W Dobereiner in 1829 made an attempt to classify elements. He observed that some group of 3 elements (triad) showed similar physical and chemical properties.

STATEMENT:

The atomic mass and properties of the middle elements is approximately the arithmetic mean of the other two elements.

SN ELEMENTS ATOMIC MASS ARITHMETIC MEAN1 Lithium 7 7+39=232 Sodium 233 Potassium 39

Although Dobereiner’s concept of triad provided background to seek further information for classification of elements but it was rejected because all elements couldn’t be arranged in such triads.

NEWLAND’S LAW OF OCTAVES:

An English chemist john new land in 1866 made next attempt to classify known elements and arranged them in the increasing order of their atomic weight.

He observed that properties of the elements are repeated after every eight element.

STATEMENT:

Chemically similar elements reoccur in octaves when arranged in order of increasing atomic weight.

Li = 7 Be = 9.4 B = 11 C = 12 N = 14 O = 16 F = 19Na = 23 Mg = 24 Al = 27.3 Si = 28 P = 31 S = 32 Cl = 35.5K = 39 Ca = 40

This law provided a basic that elements with similar properties arranged into groups (tabular form) but noble elements were included so it was rejected

ADVANTAGES:

This law provided a basic for the classification of elements into group of elements having similar properties.

This law provided a wider scope to arrange all known elements into tabular form.

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DISADVANTAGES:

The periodic arrangement of element didn’t included noble gases because the were not discovered.

MENDELEEV’S CLASSIFICATION OF OPERIODIC TABLE:

Russian chemist Dmitri Mendeleev in 1869 produced his arrangement in a form of periodic table in which elements are arranged in the ascending order of their atomic weight.

He arranged elements into 7 horizontal rows called periods and 8 vertical column called groups, element in the same group were found posses similar properties and formed similar compounds.

On this basis the proposed a periodic law

STATEMENT:

Properties of elements are periodic function of their atomic weight.

CHARACTERISTICS OF MENDELEEV’S PERIODIC TABLE:

1- Different curves and observed that elements with similar properties occupied similar position in the curve.

2- e.g. alkali metals occupy peak position halogen and acidic oxide occupy ascending position in the curve.

3- His classification couldn’t receive proper attention because of two reasons worked only on physical properties like brittleness malleability etc.

4- Mendeleev proposed his classification in the same year with separable prediction of discoveries.

5- He arranged elements in 7 horizontal rows called period and 8 vertical columns called groups.

6- His classification provides systematic way to study of elements.

DRAWBACK, S OF MENDELEEV PERIODIC TABLE:

1- No position is assigned to isotopes in different group.2- He failed to give any idea about atomic structure as his table was based on atomic mass.3- He placed some dissimilar elements in a group together e.g. alkali metals were placed with

coinage metal (cu, Ag, Au).4- Certain elements of higher atomic weight precede other with lower atomic weight Ar (39.9) precedes k (39) Co (58.9) precedes Ni (58.6) Mendeleev left certain gaps in periodic table for the element to be discovered.

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Mendeleev corrected the atomic mass of few elements e.g. atomic mass of be was corrected form 13 to 9.3 then and heavier elements could not be accomodalid

LOTHER MEYER’S CLASSIFICATION:

German chemist Luther Meyer in 1869 proposed a periodic arrangement which include 56 elements.

He plotted the values of certain physical properties and obtained

Te (127.6) precedes I (126.9)

The lanthanides a raise earth metals and actinides do not find any appropriate places in the periodic table.

He did explain the cause of periodicity.

Certain chemically similar elements e.g. cu, au, pt are placed in different groups.

MOSELEY,S CONTRIBUTION IN CLASSIFICATION “OR” MODREN PERODIC LAW:

A British physicist Mosley in 1913 (after discovery of atomic structure) established that atomic number is the fundamental property of the elements.

He succeeded to reveal a relationship between properties and atomic number of elements and modify Mendeleev’s periodic law as.

STATEMENT:

The properties of the elements are the periodic function of their atomic number ORPhysical and chemist properties of the elements are the function of their electronic configuration which varies with the increasing atomic number in a periodic manner

PERIODICITY OF THE PROPERTIES:

The repetition of the properties after definite intervals when the elements are arranged in order of increasing atomic number

PERIODIC TABLE:

It is an arrangement in such a way that elements are arranged in the increasing atomic number and elements have similar properties automatically fall in same group

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SNMENDELEEV’S PERIODIC

TABLESN

MODERN PERIODIC TABLE

1It was based on the atomic weight of elements

1it was based on the atomic number of elements

2It failed to specify the position of isotopes

2It has specified position of isotopes

3It placed coinage metal with alkali metals

3It placed coinage metal in and alkali metal in IA

4It failed to explain the structure of atom

4 It explain structure of atom

LONG FORM OF PERIODIC TABLE:

Properties of elements change in periodic manners the atomic number increasing from one inert to next inert gas.

Tabular arrangement following album principle is called long from of periodic table it is on the basis of electronic configuration

PERIODS:

The horizontal rows from left to right in the periodic table are called periods. There are seven periods in the periodic table which start from alkali metals and ends at noble elements.

PERIOD-1:

This period corresponds to filling up k-shell It is shortest period and contains only two elements H and he with electronic configuration S and is respectively.

PERIOD-2:

This period corresponds to filling up L-shell it is first short period and contain 8 elements from Li to Ne. In this period as occupy 2s and 2p orbital.

PERIOD-3:

This period corresponds to filling up M-shell. It is 2nd short period and also contains 8 elements from Na to Ar. In this period as occupy 3s and 3p orbital

PERIOD-4:

This period corresponds to filling up N-shell. It is 1st long period and contain 8 elements from k to kr. n this period as occupy 4s followed by 3d and 4p orbital.

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PERIOD-5:

This period corresponds to filling up O-shell. It is 2nd long period and also contain 18 elements from Rb to Xe in this period as occupy 5s followed by 4d and 5p orbital.

PERIOD-6:

This period correspond to filling up p-shell. It is longest period and includes 2 elements from s-block, 10 elements from d-block, 14 elements from f-block, and 6 elements from p-block. It starts as start from Cs and ends at Rn in this period as start filling 4f orbital after 5d accommodates 1e.

PERIOD-7:

This period corresponds to filling up q-shell. It is incomplete period and includes 2 elements from s-block, 10 elements from d-block 14 elements from f-block (Actinide). It starts from Fr and is incomplete. In these period es starts filling 5f orbital after 6d accommodates 1e.

GROUP:

The vertical column from top to bottom in the periodic table is known as group. There are eight group in the periodic table and these group are sub divided in to 2 groups or family or sub group A and family or sub group B.

SUB GROUP A:

The normal elements are included in sub-group A. it includes IA to 5A and also known as representative or typical elements.

SUB GROUP B:

The transition elements are placed in sub group B. It included IB to 5b.

PROPERTIES OF GROUP:

In a group of periodic table the elements contain same type of properties. They have same valence shell configuration.

PROPERTIES OF PERIODS:

The properties of elements vary gradually from left to right. The number of periods also indicates the total number of shell in all elements in the period.

TYPES OF ELEMENTS ON THE BASIS OF ELECTRONIC CONFIGURATIOIN:

This classification is based upon the type of atomic orbital which receive the last electron in its atom.There are two types of elements in the periodic table i.e. Representative and transition which are further classified as S, p and d, f respectively.

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REPRESENTATIVE ELEMENTS:

Elements of sub group “A” are called representative elements or typical elements. Metals, non metals and metalloids are included some are paramagnetic some are diamagnetic S and P block are included.

S-BLOCK ELEMENTS:

The incoming electrons enter the outermost s-orbital in the atoms of these elements. They have valence shell electronic configuration ns1and ns2 and belong to the group IA and 2A respectively:

P- BLOCK ELEMENTS:

The incoming electrons enter the outermost p-orbital in the atoms of p-block elements. Their valence shell configuration varies from ns2, np1 to ns2, np6 these elements belong to group 3A-3A.

NOBLE ELEMENTS:

Members of group 3a are known as noble elements or zero group found at the end of each period.

They are colorless gases, uncreative (inactive) and diamagnetic and their electronic configuration is exceptionally stable i.e. ns2, np6, with the exception of he (z = 2) i.e. ns2

TRANSITION ELEMENTS:

Elements of B-sub group of the periodic table are called transition elements. Only metals are included. Both paramagnetic and diamagnetic are included d and j block are included.

D-BLOCK ELEMENTS:

The incoming last electrons enter the (n-1)d-orbital in the atoms d-block elements. Their valence shell configurations varies from ns2,(n-1)d – ns2,(n-1)d10. These elements belong to the group IB-5B. They are also known as outer transition elements.

They consist of four transition series each series consist of 10 elements i.e.

1st transition series (sc-zn)2nd transition series (y-cd)3rd transition series (la-hg)4th transition series (ac-)

F-BLOCK ELEMENTS:

The incoming last electrons enter the (n-2)f orbital in the atoms of f-block elements. Their valence shell configuration varies from ns1,(n-1)d1,(n-2)f1-ns2,(n-1)d1,(n-2)f14.These elements belong to group 3 b. They are also known as inner transition elements.

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CHAPTER # 02HYDROGEN

POSITION OF HYDROGEN IN PERIODIC TABLE:

Elements are arranged in the periodic table on the basis of their electronic configuration and to some extent on the basis of their properties.

But there is no exact position of hydrogen in the periodic table. It has some resemblance and some disresemblance with IA, 7A group.

POSITION OF HYDROGEN IN IA:

SIMILARITIES:

1- Both electronic configuration end at S’.2- Both have tendency to lose one electron and from monovalent positive ion.3- Valence of group IA and hydrogen is 1.4- Both can react with non-metals.

H2+CL2----2HCL 2NA+CL2---2NaCL

5- Both act as reducing agent.6- During electrolysis, both can be reduced at cathode.

DISSIMILARITIES:

1- Hydrogen is a gas but the elements of group IA are metals at room temperature.2- Hydrogen exists as diatomic from while alkali metals exist as monatomic from.3- Elements of group IA are electropositive in character they only form ionic compound while

hydrogen is electropositive as well electronegative, so it can form ionic as well as covalent compound.

4- Alkali metals freely exist as caution in aqueous solution while H+ is not freely and exists as oxonium ion H3O+

5- Hydrogen gains electron and form – ve ion.6- While IA group elements don’t form – ve ion.

POSITION OF HYDROGEN IN 5A:

SIMILSRITIES :

1- Valance shell configuration of both hydrogen and group 5a is half filled.2- Both are non-metals.3- Both can form covalent bond.4- The thermoelynamic values of both are same

DISIMILARITIES:

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1- Elements of group 5A are solids while hydrogen is gas.2- Hydrogen is monovalent while 4a gp is tetravalent.3- Electronic configuration of 4A group ends on ns2,np2 while of hydrogen ends on ns’.4- Hydrogen exists in diatomic form while 4a group elements exist in monatomic form.5- Hydrogen requires 1 e to complete its valence shell while 4 a group require 4 es.6- Elements of group 4 a can only form covalent compounds while hydrogen can form both

ionic and covalent compounds.

POSITION OF HYDROGEN IN 7A:

SIMILARITIES:

1- Both are non-metal.2- Both are gases, exist in diatomic molecule e.g cl2,h2.3- Valence of both is 1.4- Both require 1 e to complete their valence shell.5- Both can form –v e ion, as hydrogen form hydride and halogen form halide.6- Both can react with alkali metals.

H2+NA----NAH (sodium hydride) CL2+2NA---2NaCl (sodium chloride)

DISSIMILARITIES:

1- Electronic configuration of 7 a group ends on ns2 npo2 while hydrogen ends on ns’. 2- Hydrogen contains 1 e in its valence shell while 7 a group contain 1 es3- Monovalent negative ions of halogens i.e. cl-, Br- etc. exist freely in aqueous solution while

monovalent negative ion of hydrogen (H-) is incapable to exist in water. Since, H2 is formed immediately.

H-+H2O-----OH-+H2

4- Hydrogen is electropositive and electronegative as well while halogens are only electronegative.

5- Electron affinity of hydrogen is much less as compassed to group 7 A.

CONCLUSION :

From the above discussion, we conclude that position of hydrogen in the periodic table is still unsatisfied and because of its simplest nature hydrogen shows different behavior.

INDUSTRIAL PREPARATION OF HYDROGEN:

ELECTROLYSIS OF WATER:

Water is a bad conductor of electricity therefore we have to add any electrolyte (acid, base or salt) to pass electricity through water.

As result hydrogen is evolved from cathode oxygen form anode.

4H2O electricity 4H* +4OH

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Rxn at cathode 4H* +4E- ------2H2

Rxn at anode 4OH- -----O2+2H2O+4EOver all rxn 2H2O -----2H2+O2

This method is used only where electricity is available at cheaper rate

STEM AND HYDROCARBON PROCESS:

When mixture of natural gas is passed over steam at 900c in the presence of catalyst Ni, it produces a mixture of H2 CO gas known as water gas.

CH4+H2O 900c 3h2+coNi (water gas)

ACTION OF STEM ON COAL: (BOSCH PROCESS):

When steam is passed over red hot coke at about 1000c a mixture of H2 and co (water gas) is formed.

C+H2O -------- H2+CO (water gas)

SEPARATION OF HYDROGEN FROM WATER GAS:

Following are two methods to repartee hydrogen from water gas.

ACTION OF STEAM:

H2 gas is separated from mixture of water gas by heating it with more steam at 500c in the present of Fe2O or Cr2O3

As a result co is converted in to CO2 and more hydrogen is produced.

H2+CO+H2O FeO CO2+2H2

CO2 is soluble in water and can be separated easily by dissolving it in water under pressure

BY LIQUIFICATION:

H2 gas is also separated from water gas by cooling it at -200c with the help of liquid air co becomes liquid hydrogen is separated.

Traces of co further removed by passing it through Na oh which absorb CO

CO+ Na OH---------N C O O Na Sodium format

STEAM METHANOL PROCESS:

When mixture of methanol and steam is heated at 250c mixture of co2 and H2 produced.

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CH3OH + H2O ----250c CO+3H2

CO2 is separated by passing the mixture through water under high pressure, where by CO2 will dissolve in water and free H2 gas is obtained.

THERMAL DECOMPOSITION OF HYDROCARBON:

When natural gas is heated in the presence of O2 it decompose to form carbon black and hydrogen gas

CH4 700c---------2H2+C

Carbon black is rubber, tire, ink pigment plastic and used typewriter ribbon, carbon paper etc manufacturing.

THERMAL DECOMPOSITION OF AMONIA:

When vapors NH3 is heated at 1000c in the presence of active catalyst , it produce mixture of H2 and N2 gas.

2NH3 1000c N2+3H2

Catalyst

When above mixture is cooled at – 196c N2 becomes liquefy and H2 gas is obtained.

ATOMIC HYDROGEN:

The product obtained by the dissociation of molecular hydrogen is known as atomic hydrogen to dissociate molecular hydrogen 104k cal mol-1 bond energy is required.

PREPARATION OF ATOMIC HYDROGEN:THERMAL DECOMPOSITION OF HYDROGEN MOLECULE:

When we hydrogen gas is heated up to 5000c, it dissociates into atoms.H2+104 KCL 5000c 2H

BY ELECTRONIC DISCHARGE:

When electricity is passed through hydrogen gas at low pressure, atomic hydrogen is produced.

H2 electric discharge------ 2HImm-0.1mm pressure

PROPERTIES:

Atomic hydrogen is more reactive than molecular hydrogen. Its rxn take place at ordinary temperature.

REACTION WIYH NON-METALS:

P+3H--------PH3

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O2+2H-------H2 O2

S+2H-------H2 S CL2+2H-----2HCL

REACTION WITH METALS:

Ca+ 2H--------CaH2

Na+ H---------Na H

REACTION WITH OXIDES:

Cu O+ 2H------Cu+H2OHg O+ 2H------Hg+H2 OAg Cl + H---------Ag+ H Cl

STABILITY:

Atomic hydrogen is highly unstable they instantly combine to convert molecule.

USES:

1- Chemically atomic hydrogen is used in laboratory as powerful reducing agent.2- Atomic hydrogen is used to produce atomic hydrogen torch.

Some alloys of Ni, Cr, Al melts at 4000c-5000c for welding these alloys a flame of high temp is required this flame is produced by Atomic hydrogen torch.

PRINCIPLE:

When hydrogen gas is passed through an electric are set b/w tungsten rods. It splits in to atomic hydrogen which combines to convert molecular hydrogen release 104k.cal/mol/energy which produces flame of 4000c-5000c.

NASCENT HYDROGEN:

The newly born hydrogen which is produced during chemical reaction is called nascent hydrogen.

OR

The hydrogen produced at the moment of its chemical production is called nascent hydrogen.

REACTIVITY OF NASCENT OR ATOMIC HYDROGEN:

Nascent as atomic hydrogen are very reactive as compare molecular hydrogen.

CH3 Cl+ H2-----------no rxnCH3 + 2H------------CH4+HCl

ATOMIC HYDROGEN:

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1- It is formed by the decomposition of 2- Molecular hydrogen in to atomic 3- Hydrogen

H2 electric are 2 H Zn+2HCl-----Zn cl+2 H

NASCENT HYDROGEN:

1- It is formed by the chemical 2- Reaction or during a chemical rxn

BINARY COMPOUND:

The compound which is formed by the combination of two elements is known as binary compound.

BINARY COMPOUNDS OF HYDROGEN OR HYDRIDES:

The binary compounds formed by the combination of hydrogen and other elements are called hydride.

CLASSIFICATION OF HYDRIDE:

On the basis of bond hydride are classified into following.

IONIC HYDRIDE:

The hydride which is formed by the transference of electron from metal atom to hydrogen atom is known as ionic hydride.

Ionic hydride are formed by group I A and 2 A except Be and Mg.

They have salt like character so also known as salt like or saline hydride.

PREPARATION:

When hydrogen gas is passed through red hot alkali and alkaline earth metal, ionic hydrides are formed.

2Na+H2------200c ---2NaH Ca+H2-------200c----CaH2

PROPERTIES:

1- They are colorless, non-volatile salt like solids having high melting point.2- They are sufficiently stable towards heat, stability decreases with increasing atomic masses.3- They contain cubic structure.4- They are insoluble in organic solvents but soluble in water with which they react and

produce hydrogen.

Ca H2+ H2O --------CA (OH) + 2H2

Na H + H2O---------Na OH + H2

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They also produce hydrogen on reaction with acid and alcohols.

USES:

1- They are used as a source of producing H2.2- They used as reducing agent in metallurgical process.3- They are used as dehydrating agent for organic solvent.

COVALENT HYDRIDE:

The hydrides which are formed by mutual sharing of electrons is known as covalent hydride.Covalent hydrides are formed by group 3 A-7 A.

PREPARATION:

They can be prepared either by direct method or by indirect method.

DIRECT METHOD:

H2+ Cl2 sunlight--------2HClH2+ S sunlight---------H2 S

INDIRECT METHOD:

CaC2+ 2H2O---------Ca (OH) 2+C2 H2

Hl4 C3 6H2 O-------2AL2O3+3CH4

PROPERTIES:

1- They are colorless gases or volatile liquid having low boiling point except water which has high B.P due to presence of intermolecular hydrogen bond.

2- Hydrides of group 3 A and 4A are neutral3- Hydrides of group 5A are basis.4- Hydrides of group 6 A and 7A are acidic.5- Stability of these hydrides decreases with the increase in size of non-metal atoms.

COMPEL HYDRIDE:

Hydride of group 3A are not stable so they combine with hydride of group I A and form such hydrides in which all three types of chemical bonds i.e ionic, covalent and co-ordinate covalent bond are present.

They aren’t binary so they are known as complex hydride.They have general formula A B H 4Where A= univalent ion = LI*, Na* etc B=trivalent ion = B*3, Al*3

PREPARATION:

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LiH+AlH3---------LiAlH4

NaH+BH3---------NaBH4

PROPERTIES:

1- They are salt like white solid.2- They are stable at 300c.3- They have tetrahedral structure.4- They are powerful reducing agent.5- When they are dissolved in water, they produced hydrogen gas.

LiAlH4+4H2O------Li OH +Al (OH) +4H2

METALLIC HYDRIDE:

Hydrogen forms hydrides with transition metals, properties of these hydrides are apparently as pure metals, therefore they are named as metallic hydride.

In there hydride hydrogen occupied interstitial spaces so they are also known as interstitial hydride.

PROPERTIES:

1- These hydrides are non stanchion metric no true chemical bond is present.2- E.g. LaH2.75, VH 0.563- They are good reducing agent.4- They hydride are used as catalyst in the hydrogenation rxn.

CH3 Cl +2H -----Ni----CH4+ HCl

POLYMERIC HYDRIDE:

Be and Mg of 2A group react with hydrogen form hydride with formula BeH2 and MgH2 respectively these hydride then polymerized to form (BeH2) and (MgH2) n. Therefore they are known as polymeric hydride.

Their properties are intermediate between ionic and covalent.

BORDER LINE HYDRIDE:

This hydride is formed by metals of group IB, 2B and some metals of group 3A such as In, Te.

Example:

Cu H2, ZnH2, InH2, TlH2.

They are unstable hydrides.They properties are intermediate between metallic and covalent hydride.

ISOTOPES:

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Atoms of same elements having same atomic number but different mass number”

OR

Atoms that have same number of protons but different number of neutrons are known as isotopes”

ISOTOPES OF HYDROGEN:

There three isotopes of hydrogen.

PROTIUM:

1. It is also known as ordinary hydrogen.2. It contain1 electron in the k-shell,1 proton in the nucleus while it does not have neutron.3. Its relative abundance in 99.98/ 4. Its atomic number is 1 and mass number is 1 as well.5. It is symbolized as H or P.

DEUTRIUM:

1. It is also known as heavy hydrogen.2. It contains 1 electron in k-shell and 1 proton and 1 neutron in the nucleus.3. It is relative abundance is 0.0156%.4. Its atomic number is 1 and mass number is 2.5. It is symbolized as H2 or D.6. When deuterium reacts with oxygen it forms heavy water (D2O).

TRITIUM:

1. It is also known as radioactive hydrogen.2. It contains 1 electron in k-shell and 1 proton and 2 neutrons in the nucleus.3. It’s relative abundance is 4*10 %4. Its atomic number is 1 and mass number is 3.5. It is symbolized as H3 or Y3.6. Its half life is 12.5 years.

CHAPTER # 03S-BLOCK ELEMENT

DEFINITION:

The elements in which last electrons enters in ns orbital are called S-Block elements. The elements of group IA and group IIA in the periodic table are S-Block elements the elements of group IA are called alkali metals including the following elements Sodium (Na), Lithium (Li), Potassium (k), Rubidium (Rb), Cerium (Cs) and Francium (Fr) the elements of group IIA are called alkali earth metals Beryllium (Be), Magnesium (Mg), Calcium (Ca), Scandium (Sr), Barium (Ba) and Radium (Ra) are the numbers of group IIA.

Why elements of group IA are called alkali metals?

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The elements of group IA have ability to form alkalis their oxides and hydroxides are alkalis in nature so they are called alkali metals.

Why elements of group IIA are called alkaline earth metals?

The elements of group IIA are exist as in oxides form in the earth and their oxides and hydroxides are also are also alkaline in nature so they are called alkaline earth metals.

GROUP TRENDS IN S-BLOCK ELEMENTS:

The regular variation in the properties of elements is known as Group trends for e.g. electro negativity ionization potential atomic radii, hydration energy melting & boiling point etc. the group trends in physical property are discussed below.

ELECTRO NEGATIVITY:

The tendency of an atom to although a shaped pair of electron towards itself is known as electro negativity

IN GROUP:

In group as we make from top to bottom the electro negativity decreases due to increase in atomic size.

Comparison between electro negativity alkali & alkaline

EARTH METALS:

Alkaline earth metals are making electro negativity as compare to alkali metals due to their smaller atomic size and high nuclei charge

IONIZATION POTENTIAL:

The minimum amount of energy required to remove an electron from garners atom is called ionization potential

IN GROUP:

Ionization potential decreases as use moke down the group because in group atomic size increases and due to increase in atomic size the distance between nuclei and outer most electrons also increases so the attraction between and outer most electrons becomes lower so the ionization potential decreases in down the group alkali earth metals have high ionization potential as compare to alkali metals because of lower atomic size and higher nuclei charge.

The second ionization enthalpy of alkaline earth metals are higher them first ionization enthalpy because when first electron has been removed them nuclei charge an atom is increases and interaction between nucleus and outer most electron is also increase so he second electron require more energy for removed and hence the second ionization enthalpy is higher than the first in alkaline earth metal.

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ATOMIC RADII:

The distance from the centre of nucleus to the outer most shell is called atomic radius

IN GROUP:

As we moke from top to bottom in a group the atomic radii increases due to increase in number of shells

Alkaline earth metals have smaller atomic radii as compare to alkali metals because of their high nuclei charge.

IONIC RADII:

The distance from the centre of nucleus to the outer most electron in as atom is called ionic radii alkali and alkaline earth metals are highly electro positive so they can easily from positive ion (Lation) the size of the Lation (M+1) is less then as compare to the size of metal (M) the reason is that when an atom loses electron then the number of electrons becomes decreases as compare to the number of protons so the nuclei charge increases and now the attraction between nuclei and the outermost electrons increases due to which the size of the ion because shrink.

Hydration energy:

The amount of energy released in the formation of hydrate of one mole of M+(g) ion is called hydration energy

M+(g) + aq = [M(ar)]+ + Energy released

IN GROUP:

Hydration energy depends upon size of the atom as we moke down the group hydration energy decreases because of increasing in atomic size alkaline earth metals are easily hydrate as compare to alkali metals because of their lower atomic size and higher nuclei charge.

ELECTRODE POTENTIAL:

The difference of potential created between a metal and solution of its salt is called electrode potential it is the measure of a tendency of an electrode to lose (or gain) electron. The elements which have higher value of redaction potential they can easily reduced and are oxidizing agent while these elements which have lower values of reduction potential they can easily oxidized and are reducing agents.

Alkali and alkaline earth metals have very low reduction potential values so they act as a powerful reducing agent. Alkali and alkaline earth metals cannot be used in voltaic cells because their reduction potentials are very lower and they are powerful reducing agents they reduced the water present in voltaic cells

MELTING & BOILING POINTS:

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Alkali metals have lower melting & boiling point because they have only one electron in their valence shell and atoms are bonded by single valence electron so the inter atomic forces are weak and they have low melting & boiling points. Alkaline earth metals are harder than alkali metals because alkaline earth metals have high nuclei charge as compare to alkali metals and inter atomic forces are strong so they have high melting & boiling points as compare to alkali metals.

CHEMICAL PROPERTIES OF S-BLOCK ELEMENTS

Alkali and alkaline earth metals are very reactive they combine directly with main metals for e.g.

Reaction with halogen:

Alkali and alkaline earth metals reacted with halogen and forms halides

2Na + Cl2 2NaClMg + Cl2 MgCl2

Reaction with hydrogen:

Alkali and alkaline earth metals reacted with water and forms their hydrides

2Na + H2 2NaHCa + H2 CaH2

Reaction with nitrogen:

Alkali and alkaline earth metals reacted with nitrogen and forms nitrides

6Na + N2 2Na3N3Mg + N2 Mg3N2

Reaction with water:

Alkali and alkaline earth metals reacted with water and produces hydroxides of them

2Na + H2O 2NaoH + H2

Ca + H2O Ca (OH) 2 + H2

Reaction with oxygen:

Alkali and alkaline earth metals directly combine with oxygen and producing a variety of oxides (O-2), peroxides (O-2

2) and super oxides (O-12) the type of product depends upon the type of metal

and temperature.

2Na + O2 2Na2O (sodium peroxide)2Na + O2 Na2O2 (sodium peroxide) Na + O2 NaO2 (sodium superoxide)Ba + O2 BaO2 (barium peroxide)2Ba + O2 2Bao (barium oxide)

EXTRACTION OF METALS:

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The alkali metals:

Alkali metals are very reactive metals so they do not occur in nature in free state they are obtained from their compounds

MANUFACTURE OF SODIUM BY DAWN’S PROCESS:

In this process molten sodium chloride is used for electrolysis and CaCl2 is added in the molten sodium chloride for layering the melting point of sodium chloride the process is carried out in Down’s cell.

Down’s cell is made up of steel lined with fire bricks anode is made up of graphite and iron cathode is surrounded by it the two electrodes are separated by a cylindrical iron gauze diaphragm this diaphragm prevents the mixing of produced Na and Cl2 when electricity is passed through the mixture of formed NaCl CaCl2 NaCl ionizes to give Na+ and Ce-

NaCl Na+ + Cl-

Cl- discharge at anode in the form of chlorine gas (Cl2)

At anode:

Cl- le- + ClCl + Cl Cl2

At cathode sodium (Na+) discharge and produces sodium metal (Na) due to it low density it rises up and stored in the inverted through in the molten state

At cathode:

Na+ + le- Na

Over all reaction:

2Na+ 2Cl- 2Na + Cl2

COMPOUNDS OF S-BLOCK ELEMENTS:

Sodium chloride NaCl:

Sodium chloride can be obtained by two sources 1- from sea water2- from rock salt

FROM SEA WATER:

In tropical region the sea water in put into large tank and water is evaporated by solar heat and salt can be separated while in cold countries it is allowed to freeze pure water freezes to ice first NaCl remains in the solution the ice is separated and solution is evaporated to get NaCl

FROM ROCK SALT:

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The salt is mined as solid or pumped from underground deposits as saturated solution called brine by flooding underground salt beds with water by boring

PURIFICATION:

NaCl so obtained contains impurities such as calcium and magnesium these impurities and removed by treating brine with Na2CO3 and NaOH to participate these metals

CaCl + Na2CO3 CaCo3 + 2NaClMgCl2 + 2NaOH Mg (OH)2 + 2NaCl

Soluble barium chloride is used to participate sulphates

SO-24 + BaCl2 BaSO4 + 2Cl-

USES OF NaCl:

1- NaCl is an essential part of our diet 2- It is used for the perseveration of food3- In chemical industry it is used for the preparation of different chemicals such as Na metals

chloride gas NaOH, Na2CO3 etc.

SODIUM BICARBONATE NaHCO3:

NaHCO3 is also known as baking soda

PREPARATION:

NaHCO3 can prepared by Ammonia Solvay process in this process first ammonia reacted with CO2 and H2O to give NH4HCO3 and the NH4HCO3 combine with NaCl and produces NaHCO3

NH3 + CO2 + H2O NH4HCO3NH4HCO3 + NaCl NaHCO3 + NH4Cl

FROM Na2CO3:

NaHCO3 can be prepared by treating saturated sodium carbonate with carbon dioxide Na2CO3 + H2O + CO3 2NaHCO3

USES:

1- Sodium bicarbonate is used as baking soda2- It is used in medicines 3- It is used as an anti aid4- It is used fire extinguisher

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SODIUM CARBONATE Na2CO3:

Na2CO3 known as soda ash and Na2CO3 10H20 is known as washing soda. Sodium carbonate is manufactured by ammonia Solvay process

Raw material and their resources:

Brine:

Brine is obtained from natural resource of common salt is saturated solutions of NaCl

Carbon dioxide:

The source of CO2 is limestone when lime stone is heated CO2 is producedCaCo3 CaO + CO2

Ammonia:

Ammonia is resourced from the solution of NH4Cl, left after the removal of NaHCO3, NH4Cl reacts with Ca (OH)2 to give ammonia

CaO + H2O Ca (OH)2

2NH4Cl + Ca (OH)2 CaCl2 + 2H2O + 2NH3

AMMONIA SOLVAY PROCESS:

This process consists of three steps

1- Ammonization of brine2- Carbonization of Ammoniated brine3- Conversion to Sodium carbonate

AMMONIZATION OF BRINE:

In this step saturated solution of NaCl i.e. brine is mixed with ammonia in ammoniating tower until the solution becomes saturated.

CARBONIZATION OF AMMONIATED BRINE:

In this step ammoniated brine is passed into carbonating tower which is called solvay tower CO 2 is entered through bottom of the tower the CO2 and ammonia reacts to give ammonia bicarbonate (NH4HCO3) and then NH4HCO3 combined with NaCl to give sodium bicarbonate.

2NH3 + CO2 + H2O 2NH4+ + CO-23

CO-23 + CO2 + H2O 2HCO-

3

NH4+ + HCO-3 NH4HCO3

NaCl + NH4HCO3 NaHCO3 + NH4HCl

The perspective of NaHCO3 is removed by filtration and washed

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CONVERSION TO SODIUM CARBONATE:

In this step sodium bicarbonate is heated as a result of heating sodium carbonate is formed

2NaHCO3 Na2CO3 + H2O + CO2

Na2CO3 is re-crystallized from hot aqueous solution and procedure deca hydrate sodium carbonate (Na2CO3 10H2O) which is known as washing soda

AMMONIA SOLVAY PROCESS:

USES:

1- Na2CO3 is used industry for making soap, paper and detergents2- Sodium carbonate is used for manufacturing of glass and water glass3- Washing soda is used as water softener4- Sodium carbonate is used for manufacturing of different chemicals such as NaOH and

NaHCO3 etc.

SODIUM HYDROXIDE NaOH:

Sodium hydroxide in generally known as castic soda it is prepared by Castner-Kellner’s process in industry

CASTNER KELLNER’S PROCESS:

In this process saturated of NaCl i.e. brine is used for electrolysis. Castner Kellner’s cell is made up of steel anode is made up of graphite white cathode is a steam of flowing mercury as the electric current is passed through solutions of NaCl the NaCl ionizes to give Na+ and Cl- Cl- discharged at anode in the form of chlorine gas (Cl-) sodium ions are liberated at cathode where it is reduced to metallic sodium the sodium metal dissolves in mercury and forms sodium amalgam (Na/Hg) sodium amalgam is sent to another chamber where reacts with reacter and forms sodium hydroxide (NaOH) and hydrogen gas (H2)

NaCl Na+ + Cl-

Reaction at anode:

Cl- le- + ClCl + Cl Cl2

Reaction at cathode:

Na+ + le- NaNa + Hg Na/Hg2Na/Hg + 2H2O 2NaOH + H2 + Hg

ADVANTAGES OF THE PROCESS:

1- This process gives product of high purity

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2- The reaction between NaOH and Cl2 is avoided by obtaining NaOH & Cl2 in separate chambers.

DISADVANTAGES OF THE PROCESS:

1- In this process mercury is used as a cathode so the same vapors of mercury escape from the industry and contaminates sea water.

CHEMICAL PROPERTIES:

1- Sodium hydroxide (NaOH) is a strong base reacted with acid to from salt and water

NaOH + HCl NaCl + H2O

2- Sodium hydroxide (NaOH) reacts with ammonium salts on heating and librates ammonia

NH4Cl + NaOH NH3 + NaCl + H2O

3- Sodium hydroxide (NaOH) with metal salts and participated as hydroxides

FeCl3 + 3NaOH Fe(OH)3 + 3NaCl

4- When participated hydroxides are amphoteric they re-dissolve in excess of NaOH forming complex ion e.g.

Zn+2 + 2OH Zn(OH)2 (amphotenic hydroxide)Zn(OH)2 + 2OH (Zn(OH)4)-2 (complex ion)

USES:

1- NaOH is used in soap industry for manufacturing of soap and detergents2- It is used in petroleum industry for refining of petroleum3- It is used in textile industry for bleaching and dyeing process4- It is used in the preparation of different chemicals

COMPOUNDS OF ALKALINE METALS:

(i) MAGNESIUM SULPHATE : (MgSO 4)

Magnesium sulphate occurs in nature as Kieserite (MgSO4.H2O). It can be prepared by following reactions.

PREPARATION:

Mg + H2SO4 → MgSO4 + H2

MgO + H2SO4 → MgSO4 + H2O

Mg(OH) + H2SO4 → MgSO4 + 2H2O

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MgCO3 + H2SO4 → MgSO4 + H2O + CO2

The hepta hydrated magnesium sulphate (MgSO4.7H2O) is known as Epsom salt. It is soluble in water. When heated crystalline Epsom loses water forming anhydrous magnesium sulphate.

MgSO4.7H2O → MgSo4.H2O + 6H2OMgSO4.7H2O → MgSO4 + 7H2O2MgSO4 → 2MgO + 2SO2 + O2

USES:

(i) It is used as mild purgative.(ii) It is used in ceramic and cement industry.

(ii): CALCIUM SULPHATE CaSO4:

Calcium sulphate occurs in nature as CaSO4.2H2O which is commonly known as Gypsum.

PREPARATION:

CaSO4 can be prepared by following reactions.(i) CaCO3 + H2SO4 → CaSO4 + CO2 + H2O(ii) CaCl2 + Na2SO4 → CaSO4 + 2NaCl

PROPERTIES:

(i) It is sparingly soluble solid.(ii) It produces permanent hardness in water.(iii) When Gypsum is heated at 120ºC it produces plaster of paris.

CaSO4.2H2O → CaSO4.1/2 H2O + 3/2 H2O

USES:

(i) It is used in cement industry.(ii) It is used in manufacture if H2SO4.(iii) It is used in the preparation of moulds used in surgery and castings.

(iii): BLEACHING POWDER: CaOCl2

PREPARATION:

Bleaching powder can be prepared by the action of chlorine gas on slaked lime.

Ca(OH)2 + Cl2 → CaOCl2 + H2O

REACTIONS:

(i) When bleaching powder is reacted with water it liberates chlorine gas (Cl2).

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CaOCl2 + H2O → Ca(OH)2 + Cl2

(ii) Bleaching powder reacts with acids to give chlorine.CaOCl2 + 2HCl → CaCl2 + H2O + Cl2

If acid is very diluted then hypochlorous acid is formed.

CaOCl2 + HCl → CaCl2 + HOCl (Hypochlorous acid)

(iii) It liberates chlorine on reaction with moist carbon dioxide.

CaOCl2 + CO2 + H2O → CaCO3 + H2O + Cl2

USES:

(i) It is germicide so used for the purification of drinking water.(ii) It is used for bleaching purpose.(iii) It is used for preparation of Cl2 gas and chloroform (CHCl3).

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CHAPTER # 4P-BLOCK ELEMNTS

DEFINATION:

“The elements in which last electrons in nP orbitals are called P-Block elements”.The general configuration valence of P-Block elements is ns2

, 2p1 to ns2, np6. The elements of group IIIA to VIIIA are called P-Block elements. Out of these elements, 10 elements are metals and 20 are non-metals.

GROUP TRENDS:

IN P-BLOCK ELMENTS:

The regular variation in the properties of elements is known as group trends”.The group trends in physical properties are discussed below.

(i): ATOMIC RADII:

“The distance from the centre of nucleus to the outermost electron in an atom is called atomic radius”.

IN GROUP:

The atomic radii of the elements increases as we move down the group due to increase in number of energy levels.

IN PERIODS:

In period as we move from left to right, the atomic radii of the elements decreases due to increase in nuclei charge.

(ii): IONIC RADII:

“The distance from the centre of nucleus to the outermost electron in an ion is called ionic radius”.Positive ion is always smaller than its parent atom because when electron remove from the atom then positive ion (cation) forms and in cation the number of proton is higher than number of electron so we can say that nuclei charge is higher in cation as compare to parent atom due to which the attraction of nucleus towards electron is also higher in cation and hence size of the cation become reduced. The size of an anion (negative ion) is always higher than its parent atom.The negative ions forms when an atom accepts electron so the number of electron is higher than number of proton in the anion as compare to parent atom the nuclear charge in anion is decreased so the size of an anion is higher than its parent atom.

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ELECTRONEGATIVITY:

“The tendency of an atom to attract a shared pair of electron towards itself is known as electronegativity”.

IN GROUP:

The electronegativity of P-Block element decreases in down the group due to increase of atomic size.

IN PERIOD:

The electronegativity is increases as we move from left to right in the period due to decrease in atomic size.

IONIZATION POTENTIAL:

“The amount of energy required to remove an electron from gaseous atom is called ionization potential”.

IN GROUP:

The values of ionization potential decreases in down the group except (IIIA). Ionization potential depends upon atomic size and shielding effect of inner energy level. As the atomic size and shielding effect increases down the group so ionization potential decreases.

IN PERIOD:

Ionization potential of P-Block elements increases as we move from left to right in the period. This is due to lower atomic size and low shielding effect creates greater force of attraction between nucleus and electron. Hence greater will be ionization potential.

ELECTROPOSITIVITY OR METALLIC CHARACTER:

The tendency of an atom to give out electrons is known as electropositivity. This tendency decide the metallic character, greater the tendency to give out electrons, more is the metallic character.

IN GROUP:

The metallic character increases down the group in all P-Block elements because metallic character depends upon ionization potential and electron population of outermost shells metallic character is inversely proportional to both these factors. In the group, the ionization potential and electron population decreases down the group due to which metallic character as well as electropositivity increases.

IN PERIOD:

In the period as we move from left to right metallic character as well as electropositivity decreases due to increase in ionization potential and electron population of outer most shells.

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MELTING AND BOILING POINTS:

In P-Block elements the trend of melting and boiling point in the group is not similar. The melting and boiling points depends upon various factors such as: inter atomic forces, inter molecular forces, structure or state of element.In group IIIA there is no regular variation. In group IVA there is decrease in m.pand b.p down the group due to decrease in inter atomic forces whereas form VA to VIIIA melting and boiling points increases down the group because structure gradually changes from discrete state to aggregated state (gas to solid).

BORIC ACID H3BO3

PREPARATION:

Boric acid can be prepared by following methods.

(i): FROM BORAX:

Boric acid can prepared by the action of H2SO4 on hot solution of borax.

Na2B4O7 + H2SO4 + 5H2O → 4H3BO3 + Na2SO4

(ii): FROM BORON NITRIDE:

Boric acid can be prepared by the action of super heated water on boron nitride.

BN + 3H2O → H3BO3 + NH3

(iii): FROM BORIC ANHYDRIDE:

Boric acid prepared by the hydrolysis of boric anhydride (B2O3).

B2O3 + 3H2O → 2H3BO3

PROPERTIES:

(i) It is soft, silky and white crystalline solid.(ii) It is sparingly soluble in cold water but readily soluble in hot water,(iii) It is greesy in feel.(iv) It is very weak acid.(v) It can accept a lane pair of electron so it is monoboric acid.

B(OH)3 + H2O ═══ B(OH)-4 + H+

(vi) Boric acid in heating from different products.

H3BO3 → HBO2 + H2O

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4HBO2 → H2B4O7 + H2O (pyroboric acid)

2H3BO3 → B2O3 + 3H2O (boric acid)

USES:

The aqueous solution of boric acid act as a mild antiseptic and used as an eye-wash.Boric acid is also used in glass industry.

BORAX: Na2B4O7.10H2O

Borax is known as sodium tetra borate decahydrate. It is a salt of pyroboric acid.

PREPARATION:

(i): FROM BORIC ACID:

Borax can be prepared from boric acid by the following reactions.

4H3BO3 + 2NaOH → Na2B4O7 + 7H2O

4H3BO3 + Na2CO3 → Na2B4O7 + 6H2O + CO2

(ii): FROM COLEMANITE:

Colemanite (Ca2B6O11) is an ore of borex when colemanite is boiled with concentrated solution of Na2CO3, borax is produced.

Ca2B6O11 + 2 Na2CO3 → 2CaCO3 + Na2B4O7 + 2NaBO2

PROPERTIES:

(i) It is while crystalline solid.(ii) It is soluble in water.(iii) It forms alkaline solution on hydrolysis.

Na2B4O7 + 7H2O → 2NaOH + 4H3BO3

(iv) Action of heat

Na2B4O7 + 10H2O → Na2B4O7 → 2NaBO2 + B2O3

USES:

(i) Borax is used as flux in soldering and welding.(ii) Borax is used in glass industry.

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EXTRACTION OF ALUMINIUM FROM BAUXITE ORE:

Bauxite ore having formula Al2O3.nH2OExtraction of aluminium from bauxite is consisting of three steps.

(i) Purification of bauxite to alumina.(ii) Electrolysis of alumina.(iii) Refining of aluminium.

(i): PURIFICATION OF BAUXITE:

Bauxite contains Fe2O3 and SiO2 as chief impurities. These impurities can be removed by any of the following methods depending upon the nature of impurities present in it.

(a) Hall’s method(b) Baeyer’s method(c) Serpeck’s method

(a): HALL’S METHOD:

This method is used when bauxite contain both impurities Fe2O3 and SiO2.In this method Bauxite is treated with sodium carbonate (Na2CO3). It dissolves to form sodium aluminate while the impurities are left.

Al2O3.nH2O → 2NaAlO2 + CO2 + nH2O

The solution is filtered. The filtrate obtained is heated upto 50ºC − 60ºC in presence of CO 2, the precipitate of aluminium hydroxides Al(OH)3 are formed.

2Al(OH)3 → Al2O3 + 3H2O

In this way water is evaporated and we get pure alumina.

(b): BAEYER’S METHOD:

This method is used for purification of Bauxite when excess of Fe2O3 is present in the one as impurities.In this method bauxite is treated with caustic soda (NaOH), as a result of this bauxite goes into solution as sodium aluminate and impurities remains insoluble.2NaOH + Al2O3 → 2NaAlO2 + 2(n) H2OThe solution is filtered to remove impurities. The filtrate is hydrolysed to get precipitates of Al(OH)3.NaAlO2 + 2H2O → Al(OH)3 + NaOHThe precipitate of Al(OH)3 are ignited at about 1500ºC to get pure Alumina.2Al(OH)3 → Al2O3 + 3H2O

(c): SERPECK’S METHOD:

This method is used for purification of bauxite when excess of SiO2 present as an impurities.In this method bauxite is mixed with carbon and heated up to 1800ºC in the current of nitrogen as a result of this aluminium nitride is formed.

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Al2O3.nH2O + 3C + N2 → 2AlN + 3CO + nH2OAluminium nitride (AlN) on hydrolysis with hot water produces precipitate of Al(OH)3

AlN + 3H2O → Al(OH)3 + NH3

Al(OH)3 is filled dried and ignited to get pure Alumina.2Al(OH)3 → Al2O3 + 3H2O

(ii): ELECTROLYSIS OF PURE ALUMINA:

The electrolysis is carried out in electrolytic cell made up of steel. In thjis cell anode is made up of carbon rods, suspended in the molten electrolyte and cathode is made up of carbon lining (Graphite) around the cell.The electrolyte consists of alumina dissolved in fused cryolite (Na3AlFr) and fluorspar (CaCl2). fluorspar (CaCl2) is used for lowering the melting point of alumina and when electric current is passed through the mixture, then Aluminium is obtained at cathode in liquid state from water where it is removed periodically. Oxygen is collected at anode where it reacts woth carbon anode and forms CO2. In this way anode is consumed and has to replaced.

2Al2O3 → 4Al+3 + 6O-2

AT CATHODE:

4Al+3 + 12e- → 4Al

AT ANODE:

6O-2 → 12e- + 3O2

3O2 + 3C → 3Co2

(iii): REFINING OF ALUMINIUM BY HOOP’S ELECTROLYTIC METHOD:

Aluminium obtained as a result of electrolysis of alumina is 99% pure. It is further refined by electrolysis. The electrolysis is carried out in electrolytic cell consist of iron box which is lined with carbon at bottom which act as a Anode. It contains three layers of fired mass. The lower layer consist of an alloy impure aluminium with copper. The middle layer consist of pure aluminium and serves as cathode. The three layers separated due to difference in specific gravity.When electric current is passed Al+3 ions from the middle layer migrate to the upper layer where they are reduced to aluminium. At the same time equal number of Al+3 ions are produced in the lower layer. There Al+3 ions migrate to the middle layer. Pure aluminium is tapped off from time to time. In this way 99.99% pure aluminium is obtained.

Na3AlF6 → 3NaF + AlF3

AlF3 → Al+3 + 3F-

AT CATHODE:

Al+3 + 3e- → Al(3)

AT ANODE:

Al → 3e- + Al+3

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OVER ALL REACTION:

Al+3 + Al → Al + Al+3

PROPERTIES:

(i) It is bluish white metal silvery luster.(ii) It is malleable and ductile.(iii) It is good conductor of heat and electricity,(iv) Its density is 2.7gm/ml


(i): ACTION ON AIR:

Aluminium is not affected by dry air at ordinary temperature but moist air forms a thin film of oxide on its surface.If aluminium is heated strongly in air, it forms Al2O3.

4Al + 3O2 → 2 Al2O3

(ii): ACTION OF ACIDS:

Aluminium reacts with HCl and dil H2SO4 to form H2 gas.

2Al + 6HCl → 2AlCl3 + 3H2

2Al + 3H2SO4 → Al2(SO4)3 + 3H2

Concentrated H2SO4 reacts with aluminium to give SO2 and Al2 (SO4)3

2Al + 6H2SO4(conc) → Al2(SO4)3 + 6H2O + 3SO2

Nitric acid (HNO3) does not react with aluminium due to formation of protective layer on the surface of metal. HNO3 is a strong oxidizing agent and it serve only to thicken the protective oxide coating.

(iii): ACTION OF ALKALIES:

Aluminium reacts with alkalies and forms aluminate and liberates H2 gas.

2Al + 2NaOH + 2H2O → 2NaAlO2 + 3H2

2Al + 2KOH + 2H2O → 2KAlO2 + 3H2

(iv): ACTION OF HALOGEN:

Aluminium reacts with halogens to form halides.

2Al + 3Cl2 → 2AlCl3

2Al + 3Br2 → 2AlBr3

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(v): ACTION OF NITROGEN:

Aluminium reacts with nitrogen to give Aluminium nitride (AlN).

2Al + N2 → 2AlN

(vi): ACTION OF CARBON:

When aluminium is heated with carbonit form aluminium carbide (Al4C3).4Al + 3C → Al4C3

(vii): ACTION OF WATER:

Boiling water reacts with aluminium and produced aluminium hydroxide Al(OH)3 and liberates H2

gas.

2Al + 6H2O → 2Al(OH)3 + 3H2

(viii): AS A REDUCING AGENT:

Aluminium is a strong reducing agent it reduces the oxides of most of the metals.

Fe2O3 + 2Al → 2Fe + Al2O3

This is exothermic reaction and great amount of energy is released. Due to this reaction this process is used for welding purpose. The reduction of metal oxides involving aluminium as reducing agent is termed as “thermite process”.

USES:

(i) It is used in making the house hold utensils.(ii) It is used in the manufacture of electrical transmission wires.(iii) Aluminium foil is used for wrapping chocolates. medicines, cigarettes and photographic

films.

ALUM:

“Double sulphates of monovalent and trivalent metals containing 24 molecules of water of crystallization are called Alum”.

FOR EXAMPLE:

K2SO4.Al2(SO4)3.24H2OK2SO4.Cl2(SO4)3.24H2O(NH4)2SO4.Cr2 (SO4)3. 24H2O(NH4)2SO4. Al2(SO4)3. 24H2O

POTASH ALUM OR PHITKARI:

K2SO4.Al2(SO4)3.24H2O is potash alum and commonly known as Phitkari.

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PREPARATION:

Potash alum is prepared by mixing the solution K2SO4 and Al2(SO4)3 in equimolar quantites. The solution is evaporated to saturation and allowed to cool. As a result of this crystals of alum are formed.K2SO4 + Al2(SO4)3 + 24H2O → K2SO4.Al2(SO4)3.24H2O

PROPERTIES:

(i) It is crystalline acid.(ii) It is soluble in water.(iii) At 200ºC it forms porous mass called burnt alum or phul-phitkari.

K2SO4.Al2(SO4)3.24H2O → K2SO4 + Al2(SO4)3 + 24H2O

USES:

(i) It is used in purification of water.(ii) It is used in tanning leather.(iii) It is used for sizing paper.(iv) It is used in foam type of fire extinguishes.

ALLOTROPY:

“Two or more forms of same elements having same chemical properties but different physical properties are called allotropes and this phenomenon is called Allotropy”.

ALLOTROPIC FORMS OF CARBON:

There are two allotropic forms of carbon.(i) Crystalline form(ii) Amorphous form

(i): CRYSTALLINE FORM:

(a) Diamond (b) Graphite

(ii): AMORPHOUS FORM:

(a) Coal(b) Charcoal(c) Lamp black etc

DIAMOND:

Diamond is a crystalline form of carbon.

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PROPERTIES:

(i) Diamond is the hardest known substance.(ii) It is non-conductor of electricity.(iii) In pure form it is crystalline solid.(iv) Usually pure diamonds are colarlen.(v) Diamond has high refractive index i.e. 2.45 so it acquires great brilliance.

STRUCTURE:

(i) In diamond each carbon is Sp3 hybridized.(ii) One carbon is present at the centre of tetra hedron.(iii) Each carbon atom is covalently linked with four other carbon atoms to give basic

tetrahedral unit.(iv) The arrangement of carbon is such that the structure consist of a series of hexagons.(v) Each carbon atom utilizes its four unpaired electrons in the formation of four covalent

bond.(vi) These bonding electron pairs are localized due to this reason diamond is bad conductor

of electric current.(vii) The C – C bond length is 1.54Aº and C – C bond energy is 347KJ/mol.

GRAPHITE:

Graphite is another crystalline form of carbon.

PROPERTIES:

(i) It is dark grey crystalline solid.(ii) It is soft and greasy to feel.(iii) It is good conductor of electricity.(iv) It possesses high melting point.(v) It leaves black mask on paper, so it is used in making pencils.

STRUCTURE:

(i) In graphite each carbon is Sp2 hybridized.(ii) Each carbon is covalently linked with three other carbon atoms to give basic hexagonal

ring(iii) These hexagons are arranged in parallel layers.(iv) These layers are held together by weak vender wool folks.(v) The inter layer binding energy is very low i.e. 3.99Kcal/mol.(vi) The distance between layers is 3.35Aº.(vii) In hexagonal ring C – C bond distance is 1.42Aº.(viii) The fourth electron of each carbon forms the delocalized π-bonds which spread

uniformly over all carbon atom.

Why graphite is conductor of electricity while diamond in non-conductor?

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In greater each carbon is Sp2 hybridized and fourth electron of each carbon forms the delocalized π-bonds. Due to delocalized π-bonds, graphite conduct electricity while in diamond each carbon is Sp3 hybridized and each carbon atom utilizes its four unpaired electrons in the formation of four covalent bonds. These bonding electrons are localized so, diamonds do not conduct electricity.

Why diamond is hard and graphite is soft?

In diamond each carbon atom is bonded strongly to four other carbon atoms and bond energy for each C – C bond is very high i.e. 347KJ/mol so diamond is hard. While in graphite each carbon is bonded to three other carbon atoms and forms a layer structure. These layers are held together by weak vander waal’s forces and due to large interplaner distance (3.35ºA), the layer slide easily over another that is why graphite is soft and used as lubricant.

LEAD PIGMENTS:

Lead (Pb) forms various types of pigments which are used to give the proper to paints etc. Some of them are discussed below.

(i) White lead pigment.(ii) Red lead pigment.(iii) Chrome Yellow pigment.(iv) Chrome Red pigment.(v) Turner’s Yellow pigment.

(i): WHITE LEAD PIGMENT:

FORMULA:

2PbCO3.Pb(OH)3 OR Pb3(OH)2.(CO)2

PREPARATION:

BY DUCH PROCESS:

In this process a mixture of the vapours of acetic acid and steam is passed into the chambers containing lead sheets until the corrosion of lead is complete. By passing the mixture of CO2 and vapours of acetic acid through this corroded lead, the white lead is formed on the surface of lead sheets. This product is scratched and collected.

2Pb + 2CH3COOH + 2H2O → [Pb(OH)2.Pb(CH3COO)2] + 2H2

3[Pb(OH)2.Pb(CH3COO)2] + 2H2O + 2CO2 → 2[2PbCO3.Pb(OH)2] + 6CH3COOH(ii): RED LEAD PIGMENTS:

FORMULA:

Pb3O4 OR 2PbO.PbO2

PREPARATION:

It is prepared by heating lead monoxide (litharge) in a revolving furnace with excess of air at about 450ºC.

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6PbO + O2 → 2Pb3O4

(iii): CHROME YELLOW PIGMENT:

FORMULA:

PbCrO4

PREPARATION:

(i) It can be prepared by adding solution K2CrO4 to the solution of Pb(NO3)2.

Pb(NO3)2 + K2CrO4 → PbCrO4 + 2KNO3

(ii) It can also be prepared by the action of K2CrO4 on Pb(CH3COO)2.

Pb(CH3COO)2 + K2CrO4 → PbCrO4 + 2 CH3COOK

(iv): CHROME RED PIGMENT:

FORMULA:

Pb2CrO5 OR PbCrO4.PbO

PREPARATION:

It is prepared by heating lead chromate with NaOH.

2PbCrO4 + 2NaOH → Pb2CrO5 + Na2CrO4 + H2O

(v): TURNER’S YELLOW PIGMENT:

FORMULA:

PbCl2 .4PbO

PREPARATION:

It is prepared by boiling the solution of NaCl with litharge (PbO).5PbO + H2O + NaCl → 2NaOH + PbCl2 +.4PbO

NITRIC ACID HNO3:

Manufacture of HNO3 by Ostwald’s method:

HNO3 is prepared in industries by the oxidation of NH3 by Ostwald’s process. This process consists of three steps.

(i) Oxidation of NH3 into NO.

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(ii) Oxidation of NO into NO2.(iii) Conversion of NO2 into HNO3 by absorbing H2O.

(i): OXIDATION OF NH3 INTO NO:

In this step 1 part by volume NH3 and 10 parts O2 is entered in converter which contain platinum gauge heated to a temperature of 600ºC - 800ºC. Here NH3 is oxidized into NO.4NH3 + 5O2 → 4No + 6H2O ∆H = negativeThe reaction between NH3 and O2 is reversible so, to obtained the maximum yield of NO, according to Le-chatlear principle we should follow the following conditions.

(i) Large quantity of oxygen.(ii) Low temperature i.e. 600ºC - 800ºC.(iii) Low pressure.(iv) Use of catalyst i.e. Pt.

(ii): OXIDATION OF NO INTO NO2:

In this step NO and air is entered into the oxidation chamber where NO is oxidized into NO2.

(iii): CONVERSION OF NO2 INTO HNO3:

In this step NO2 is entered into absorption chamber where water is sprayed from the top of the tower NO2 absorbs water and formed nitric acid HNO3. The nitric acid obtained by this process is 68%.

PHYSICAL PROPERTIES:

(i) It is colorless in pure form.(ii) It has sour taste.(iii) Its B.P is 83ºC and freezing point is -41.6ºC.(iv) Nitric acid is available in market in following forms.

(a) Ordinary HNO3 65% having density 1.4g/c(b) Concentrated HNO3 98% having density 1.51g/c(c) Fuming HNO3 containing dissolved oxides of nitrogen (NO2) and reddish-yellow liquid.

STRUCTURE OF HNO3:


Chemical properties of HNO3 are divided into following types.(i) Acidic properties(ii) Oxidizing properties(iii) Nitrating properties

(i): ACIDIC PROPERTIES:

HNO3 is strong acid and ionizes to give only one ionizable H+ ion so it is monobasic acid.

HNO3 → H+ + NO-3

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HNO3 reacted with bases to form salt and H2O.

NaOH + HNO3 → NaNO3 + H2O

OXIDIZING PROPERTIES:

HNO3 is strong oxidizing agent. The oxidizing properties of HNO3 is due to instability of its molecule and presence of nitrogen in its highest oxidation state of +5.

2H+1N+5O-63 → 2NO3 + H2O + [O]

REACTION WITH METALS:

Cu + 4HNO3(conc) → Cu(NO3)2 + 2NO2 +2H2O

3Cu + 8HNO3(dil) → 3Cu(NO3)2 + 2NO + 4H2O

REACTION WITH Zn:

Zn + 4HNB3(conc) → Zn(NO3)2 + 2NO2 + 2H2O

4Zn + 10HNO3(dil) → 4Zn(NO3)2 + N2O + 5H2O

4Zn + 10HNO3(v.dil) → 4Zn(NO3)2 + NH4NO3 + 3H2O

REACTION WITH Mg:

Dilute HNO3 with more active metal reduced to N2O.

4Mg + 10HNO3 → 4Mg(NO3)2 + N2O + 5H2O

REACTION WITH NON-METALS:

HNO3 oxidizes non-metals and reduces itself into NO2.

S + 6HNO3 → H2SO4 + 6NO2 + 2H2O

P + 5HNO3 → H3PO4 + 5NO2 + H2O

C + 4HNO3 → H2CO3 + 4NO2 + H2O

Si + 4HNO3 → SiO2 + 4NO2 + 2H2O

(iii): NITRATING PROPERTIES:

HNO3 replaces one or more hydrogen atoms of organic compounds with nitro group and act as a nitrating agent.

CH4 + HNO3 → CH3NO2 + H2O

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O + HNO3 → O + H2O

AQUA REGIA:

The mixture of 1 part by volume HNO3 and 3 points by volume HCl is called Aqua Regia.

3HCl + HNO3 → 2H2O + NOCl + ZCl

Aqua regia dissolve certain noble metals like gold(Au), Platinium (Pt) etc due to liberation of nascent chlorine.

REACTION OF AQUA REGIA WITH GOLD (Au):

Au + 3HCl + HNO3 → AuCl3 + NO + 2H2O

REACTION IF AQUA REGIA WITH PLATINIUM (Pt):

3Pt + 4HNO3 + 12HCl → 3PtCl4 + 4NO + 8H2O

AUTOTROPIC FORMS OF SULPHUR:

There are various allotropic forms of sulphur exist. Here we discussed some of them.(i) Crystalline Sulphur(ii) Plastic Sulphur

(i): CRYSTALLINE SULPHUR:

There are two crystalline forms of sulphur are present.(a) Rhombic Sulphur or α-Sulphur.(b) Monoclinic Sulphur or β-Sulphur

RHOMBIC SULPHUR:

PREPARATION:

Rhombic sulphur is prepared by dissolving ordinary sulphur in CS2 carbon disciplide and then the saturated solution of sulphur in CS2 is filtered nd filterate is allowed to evaporate at room temperature. After evaporation of CS2 Rhombic sulphur are obtained.

PROPERTIES:

(i) It is the stable crystalline form at ordinary temperature.(ii) It is pale yellow in color.(iii) Its melting point is 113ºC.(iv) It is insoluble in water but soluble in CS2.(v) It is non-conductor of heat and electricity.

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STRUCTURE:

(i) Rhombic sulphur consists of sulphur atoms in S8 molecules giving eight membered ring.(ii) Each S8 molecule has the form of puckered rings.(iii) In each puckered ring four sulphur atoms lie in one plane in other four atoms lie in

another plane.(iv) Each sulphure is linked to another by single bond in some ring.(v) The S – S bond distance is 2.12Aº and S – S – S bond angle is 105º.(vi) There puckered ring unite together by vander waal’s forces of attraction.(vii) These rings unite with one another and form the crystal of rhombic sulphur.

MONOCLINIC SULPHUR:

PREPARATION:

It is prepared by melting ordinary sulphur in a dish and allowing is to cool slowly until a crust is formed on the surface of another sulphur. The crust is pierced in two places with a glass rod and the liquid portion is drained out through on the holes on removing the crust, the long needle shaped crystals of monoclinic sulphur are formed on the sides of the dish.

PROPERTIES:

(i) This allotropic form of sulphur is stable only at 96ºC to 119ºC.(ii) It is insoluble in water but soluble in CS2.(iii) Its melting point is 119.25ºC.(iv) It is dark yellow transparent needle like crystals.

STRUCTURE:

(i) Monoclinic sulphur consists of sulphur atoms in S8 molecule.(ii) S8 molecules giving eight membered puckered ring.(iii) The crystals of monoclinic sulphur is needle shaped.

PLASTIC SULPHUR:

PREPARATION:

This is non crystalline allotrope of sulphur. When ordinary sulphur is heated carefully and slowly. It melts at 113ºC to a pale yellow liquid on further heating at 444.6ºC sulphur boils. If molten sulphur is passed into cold water, a soft rubber like mass is obtained called plastic sulphur.

PROPERTIES:

(i) It is non crystalline allotrope of sulphur.(ii) It is soft, sticky rubber like material.(iii) It is soluble in CS2.(iv) Its melting point is 113ºC.

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STRUCTURE:

The plastic sulphur is composed of long chains of sulphur atoms coiled up.HYDROGEN SULPHIDE: H2S

PREPARATION:

(i): FROM SULPHATE:

When sulphur is heated with hydrogen up to 6000ºC it forms H2S.

H2 + S → H2S

(ii): FROM STIBINITE: (Sb2S3)

When Sb2S3 is heated with HCl(conc), H2S is obtained.

Sb2S3 + 6HCl → 2SbCl3 + 3H2S

(iii): FROM ZnS:

When ZnS is treated with HCl, it forms H2S.

ZnS + 2HCl → ZbCl2 + H2S

(iv): LABORATORY METHOD:

In lab H2S can be prepared by the action of HCl or H2SO4 on FeS ferrous sulphide in kipp’s apparatus.

FeS + 2HCl → FeCl2 + H2S

FeS + H2SO4 → FeSo4 + H2S

PROPERTIES:

(i) It is colorless gas with rotten egg like small.(ii) It is heavier than air.(iii) It is toxic in nature.(iv) Its melting point is 86.5ºc and B.P is -60.3ºC.(v) It behave as a weak acid.


(i) H2S is a weak acid and dibasic acid, it produces two ionizable H+ ion.

H2O + H2S → H3O+ + HS-

H2O + HS- → H3O+ + S-2

(ii) H2S reacts with bases to form salt and water.

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H2S + 2NaOH → Na2S + 2H2O

(iii) It bases with air to form SO2 and water.

2H2S + 3O2 → 2H2O + 2SO2

(iv) H2S is strong reducing agent because S-2 ion loses its electrons readily to form sulphur atom and hence reduces other substances.

FOR EXAMPLE:

2FeCl3 + H2S → 2FeCl2 + S + 2HCl

REACTION WITH HNO3:

U2 + H2S → 2HCl + S

REACTION WITH HNO3:

2HNO3 + H2S → 2H2O + 2NO2

REACTION WITH H2SO4:

H2SO4 + H2S → SO2 + S + 2H2O

REACTION WITH H2O:

H2O2 + H2S → 2H2O + S

STRUCTURE:

The molecule of H2S is non-linear. The angle between H – S – H is 92.2º and the bond distance between S and H is 1.34ºA.

SULPHURIC ACID: H2SO4

Manufacture of H2SO4 by contact method:Industrially H2SO4 is prepared by contact method. This process consist of three steps.

(i) Preparation of SO2

(ii) Oxidation of SO2 into SO3

(iii) Conversion of SO3 into H2SO4

(i): PREPARATION OF SO2:

SO2 can be prepared by two methods

(a): BY BURNING SULPHUR IN AIR:

S + O2 → SO2

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(b): FROM IRON PYRITES: (FeS2)

4FeS2 + 11O2 → 2Fe2O3 + 8SO2

SO2 obtained from these methods contains same impurities which poison the catalyst so SO2 must be purified before entering in contact lower. For the purification of SO2 and air mixture is passed through special filters washing and drying towers. First SO2 and air mixture is passed through dust chamber into which steam in injected. The solid particles of impurities from droplets of water with steam and settle down. The moist gases are than dried by passing through a drying tower.

(ii): OXIDATION OF SO2 INTO SO3:

After the removal of impurities, the SO2 and air is passed through a contact chambers packed with vanadium pentaoxide (V2O5) as a catalyst. The chamber is heated upto 450ºC. Where SO2 and air combine to form SO3.

2SO2 + O2 → 2SO3 + 46Kcal

Since this reaction is reversible so for obtaining the maximum yield of SO3 we should follow the following conditions. According to Le-Chatlier principle.

(i) Low temperatire i.e. 400 - 450ºC(ii) High pressure i.e. 1.5 – 1.7atm(iii) Excess of O2

(iv) Use of catalyst i.e. V2O5

CONVERSION OF SO3 INTO H2SO4:

The SO3 produced in contact tower is passed through absorption tower. Here H2SO4 is passed from the top of the tower. SO3 is absorbed by H2SO4(conc) to form oleum.

SO2 + H2SO4 → H2S2O7 (Oleum)

Oleum is then absorbed in calculated amount of water in order to get H2SO4 of desired concentration.

H2S3O7 + H2O → 2H2SO4


(i) H2SO4 is colorless, odourless, viscous oily liquid, often known as oil of vitriol.(ii) It is hygroscopic and corrosine in action.(iii) Its boiling point is 338ºC.


The chemical properties of H2SO4 can be divided into following types.

(i) Acidic properties(ii) Oxidizing properties(iii) Dehydrating properties

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(iv) Sulphonating properties

(i): ACIDIC PROPERTIES:

H2SO4 is strong acid and it is dibasic acid because it ionizes to given two H+ ion in aqueous solution.

H2SO4 → 2H+ + SO-24

H2SO4 neutralizes the bases to form salt and water.

H2SO4 + 2NaOH → Na2SO4 + 2H2O

(ii): OXIDIZING PROPERTIES:

H2SO4 is act as oxidizing agent. The oxidizing properties of H2SO4 depends upon concentration of acid, nature of metal and temperature.Oxidizing property of H2SO4 is due to instability of its molecule. It easily decompose to give nascent oxygen which combine other compounds and oxidized them.

H2SO4 → H2O + SO2 + [O]

REACTION WITH METALS

Dilute sulphuric acid reacts with metals to give hydrogen gas and their salts.

Zn + H2SO4 → ZnSO4 + H2

Mg + H2SO4 → MgSO4 + H2

Concentrated sulphuric acid reacts with reactive metals to form different products such as:

4Zn + 5H2SO4(conc) → 4ZnSO4 + H2S + 4H2O

Metals which have less value of reduction potential, they are not oxidized by H2SO4(dil) such as Cu. Pb, Hg etc but concentrated are hot H2SO4 oxidizes these metals to form SO2 and metal sulphates.

Cu + 2H2SO4(conc) → CuSO4 + SO2 + 2H2OPb + 2H2SO4(conc) → PbSO4 + SO2 + 2H2O

REACTION WITH NON-METALS:

H2SO4 also oxidizes certain non-metals like carbon, sulphur and phosphorus.

C + 2H2SO4 → CO2 + 2SO2 + 2H2O

S + 2H2SO4 → 3SO2 + 2H2O

P4 + 10H2SO4 → 4H3PO3 + 10SO2 + 4H2O

(iii): DEHYDRATING PROPERTIES:

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H2SO4 has great affinity for water so it removes the elements of water from other compounds. This type of reaction is called as dehydration reaction.

C12H22O11 + H2SO4(conc) → 12C + 11H2O + H2SO4

Sugar

H2C2O4 + H2SO4 → CO + CO2 + H2O + H2SO4

Oxalic acid

HCOOH + H2SO4(conc) → Co + H2O + H2SO4

Formic acid

C6H12O6 + H2SO4(conc) → 6C + 6H2O + H2SO4

Glucose

(iv): SULPHONATING PROPERTIES:

H2SO4 reacts with organic compound and replaces one or more hydrogen atom and act as sulphonating agent. This process is called Sulphonation.

CH4 + H2SO4 → CH3 – SO3H + H2OC6H6 + H2SO4 → C6H5 – SO3 + H2O

USES:

(i) H2SO4 is used in the manufacture of fertilizers.(ii) It is used in the manufacture of Rayon and plastics.(iii) It is used in production of various compounds such as HCl.HF etc.(iv) It is also used in preparation of detergents.(v) It is used as dehydrating, nitrating and drying agents.

STRUCTURE OF H2SO4:

The molecule of H2So4 has tetrahedral structure as shown in the figure.

Why H2SO4 has high boiling point and high viscosity?

The high boiling point and viscosity is due to presence of hydrogen bonding in H 2SO4. Due to hydrogen bonding molecules are link together which causes high boiling point and high viscosity.

CHLORINE:

Chlorine is manufactured by two different methods in industries which are described below.

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BY NELSON’S CELL METHOD:

Nelson’s cell is v-shaped perforated steel vessel which acts as cathode. Anode is made up of graprute. In this process saturated solution of NaCl (Brine) is used in the cell for electrolysis. U-tube cathode is separated from anode by asbestos layer when electricity is passed through this solution Na+ ion moves towards cathode and deposited as sodium metal. In the same way Cl - ion move towards anode and collected in the form of chlorine gas.

CHEMICAL REACTION:

NaCl → Na+ + Cl-

AT CATHODE:

Na+ + 1e- → Na

AT ANODE:

Cl- → Cl + e-

Cl + Cl → Cl2

CASTNER-KELLNER’S CELL METHOD:

In castner – kellner’s cell method is a steam of flowing mercury. Anode are made up of graphite which are dipped in the electrolyte solution. In this process saturated solution of NaCl is used for electrolysis when electric current is passed thorugh the solution Na+ ions moves towards cathode and deposited as Na metal which dissolved in mercury to form sodium amalgam abd then reacts with water to form NaOH while Cl- ions moves towards anode and liberates chlorine gas at the anode.

CHEMICAL REACTION:

NaCl → Na+ + Cl-

REACTION AT CATHODE:

Na+ + 1e- → Na

Na + Hg → Na / Hg

2Na / hg + 2H2O → 2NaOH + H2

REACTION AT ANODE:

Cl- → 1e- + Cl

Cl + Cl → Cl2

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(i) Chlorine is greenish yellow gas with pungent smell.(ii) It is soluble in water.(iii) Its melting point is -101ºC and boiling point is -34ºC.(iv) Its density is 3.214 gm / l.


Chlorine is very reactive. It readily combines with various metals and non-metals. The reactions of chlorine can be divided into following types.

(i): OXIDATION RECTIONS:

Chlorine is oxidizing agent because it has ability to gain one electron and oxidizes most of the substances.

FOR EXAMPLE:

Zn + Cl2 → ZnCl2

Cu + Cl2 → CuCl2

2P + 5Cl2 → 2PCl5

H2 + Cl2 → 2HCl

(ii): ADDITION REACTION:

Chlorine directly combines with certain compounds to form addition products such reactions are called addition reaction.

CH2 ═ CH2 + Cl2 → CH2 – CH2

| | Cl Cl

CO + Cl2 → COCl2

SO2 + Cl2 → SOCl2

(iii): SUBSTITUTION REACTION:

Chlorine replaces one or more atoms from other compounds such reactions are called as substitution reactions.

H2S + Cl2 → 2HCl + S

2KI + Cl2 → 2KCl + I2

CH4 + Cl2 → CH3Cl + HCl

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CH3Cl + Cl2 → CH2Cl2 + HCl

(iv): AUTO OXIDATION AND REDUCTION REACTIONS:

Chlorine react with water to form hydrochloric acid (HCl) and hypochlordus acid (HOCl). In this reaction chlorine oxidized as well as reduces, it is known as self oxidation – reduction reaction or auto-oxidation – reduction reaction.

Clº2 + H+12O-2 → H+1Cl-1 + H-1O-2Cl+1

IMPORTANCE:

(i) It is used in the manufacture of various organic compounds like CCl4, CHCl3 etc.(ii) Chlorine is used as bleaching agent.(iii) It is used in sterilizing of drinking water and disinfecting drainage.(iv) It is used for the preparation of PVC.

CHAPTER # 5D-BLOCK ELEMENTS (TRANSITION ELEMENTS)

INTRODUCTION:

The elements having partially filled or f-orbital in any common oxidation state are called Transition elements

They are called for 2 reasons firstly their position in the periodic table in-between the and p-block elements and their properties are transitional between s-block elements, Which are highly reactive and strong electropositive elements forming ionic compounds, p-block elements, Which from largely covalent compounds, secondly, they show variable valiancy.

The s-block elements consist of three series each These are:

1- From scandium, se (Z=21) to zine, Zn (Z=30)2- From yttrium, Y (Z=39) TO CADMIUM, Cd (Z=48)3- From lanthanum, La (Z=57) to mercury, Hg (Z=80) The f-block elements constitute two of 14 elements each. These are:4- From cerium, Ce (Z=58) to lutetium Lu (Z=103), Which is called lanthanide series’5- From actinium, Aw (Z=89) to lawrencium lw (Z=103) Which is called Actinide series.

The d-block elements are some time called the outer and the f-block elements are called inner transition elements.

OCCURRENCE OF THE TRANSITION ELEMTS IN PAKISTAN:In Pakistan ores of few transition elements such as iron, chromium, manganese and copper have been found in the province of N.W.F.P and Balucnistan at the following places

Iron ore (Hematite) is found at mazari district kohat, at I angrial district hazara and kalabagh.Manganese ore (magnetite) is found in chaghi district and chitral state.

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Copper ores are found at saindak, zhob, pishin, laralal, in baluchistan in north waziristan agency, gilgit dir and chitral.

GENERAL CHARACTERISTICS (GROUP TRENDS):

ELECTRONIC CONFIGIRATION:

The electronic configuration of the first series of d-block elements consisting 10 elements is as under:

It is notable that in these elements the 4s orbital is complete except Cr and Cu, and the differentiating electrons enter the last but one 3d orbital. In Cr and Cu atoms, the 4s electron jumps to 3d orbital, which is due to the additional stability when d-orbital are either half-filled or completely filled.

Since valence shell of these elements generally contains the same number of electrons, thus have more or less similar physical and chemical properties generally all the transition elements are typical metals, they are brittle and good conductor of heat and electricity since the outer electrons are not bound very strongly to the nucleus.

ATOMIC OR COVALENT RAD:

With the increases of atomic number, the atomic or covalent radii of transition elements decrease from left to right across a row unit near the end the size increases slightly (from copper to zinc). On passing from left to right, the atomic size decreases due to the continuous increase. In the nuclear charge as extra positive charges are placed in the nucleus and the added electrons occupy the same shell and the orbital electrons shield the nuclear charge less effectively, which gives greater attraction of electrons towards the nucleus, hence contraction in the size of atom occurs. Thus they are smaller in size as compared to s-block elements.

IONIZTION POTENTAIAL (I.P):

The first ionization energies of first transition series vary somewhat irregularly ;they lend tend to increase from left to right .The values of I.P of transition elements are intermediate between those of s- block and p-block and elements, thus are less reactive than s- block elements and are more reactive than p- block elements they from either ionic or covalent compounds depending upon the conditions generally their compounds are ionic in lower oxidation state and covalent in higher oxidation state.

MELTING AND BOILING POINT:

The melting and boiling of the transition increase from Se to V Cr, and then decrease for Cu and Zn. In general the transition elements have very high melting and boiling point i.e. above 1000OC except Zn, W here d-orbital is completely filled. These high values are due to small atomic radii giving strong inter-atomic attraction is which in turn depend roughly on the number of unpaired d-electron in the metal atoms .At the beginning of first transition series of elements, there is one unpaired-d electrons increases in going across a period, unit Cr, after which the electrons begin pairing. Thus d-block elements are hard and have high melting and boiling points.

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VARIABLE OXIDATION STATE:

The transition elements show variable oxidation state primarily due to the fact that successive ionization energies increase gradually due to gradually due to varying involvements of the d- electrons in the bonding as very small energy difference exit between 3d and 4s orbital, therefore, electrons of 3d as well as 4s orbital take part in the bond formation. The oxidation state of the elements relate to their electron configuration. Except for scandium, this has an oxidation state of +3. Since an argon configuration is especially stable, first transition series elements show an oxidation state of +2 when both 4s electrons are involved are bonding; for oxidation state greater than +2, 3d –electrons are used in addition to both 4s electrons.

For example, Mn has an outer valence electronic configuration as d5 s2. It show a higher oxidation state of +7 in K M n O, by using two s and five d-electrons bonding. It also show an oxidation state of +2+3 and +6 in different compounds. Due to variable elements are often involved in oxidation reduction reaction.

COLOUR:

The compounds of transition elements including ionic and covalent are colored except Zn, Which is while, since electron are not be pounded d-orbital of Z +2. The color of transition elements is due to promotion of elements from one d-orbital to another, which posses small energy difference. The energy required to do this is obtained by absorbing the light of a particular wavelength in invisible of electromagnetic radiation.

The five d-orbital are oriented differently in space, an electrons (s). which is are close to legend will be repelled and hence the energy of such orbital will be raised relative to the other. T he degenerate 3d-orbital is therefore destroyed.

According to crystal field Theory (C F T), An octahedral field, split five degenerate d-orbital into two sets with different energies as follows:

1. A higher energy pair d2—Y2 and d2 z1 designated as Cg.2. A lower energy trio, dxy, dyz and d1 designated as I2g.

In many cases, the energy different between two sets (Eg and I2g) of orbital is equivalent to a wavelength in the visible rehion. Thus by absorbing visible light an electron may be able to move from lower energy set (I2g) to higher energy set (Eg) of d-orbital. In doing so some of the component wavelength of white light is absorbed. So the remaining component wavelength of the reflected or transmitted light gives an excess of the other color of the spectrum-particularly blue, so it give blue color in its compounds.

The color of a transition metals ion as associated with:

a) An incomplete 3d level (between land 9 electrons) b) The nature of legends surrounding the ion.

MAGNEYIC PROPERTIES:

Most of the compounds of transition elements are paramagnetic as they are attracted by magnetic is generally caused by the presence of unpaired electrons spin in the valence shell of the atom.

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Elements such as Fe, Co and Ni are ferromagnetic2 i.e strongly attracted in the magnetic in the field and therefore they can be magnetized.

CATALY TIC PROPERTIES:

Transition elements and their compounds are widely used as catalysts in chemical process to accelerate or retard of chemical reaction. The catalytic property is associated with their variable oxidation state, which may form unstable intermediate, and in, other cases it provides a suitable reaction surface, For example:

1- Ni is used for hydrogen of vegetable oil.2- Fe is used in the manufacture of Nh3 in Huber’s process.3- V2O2 is used for oxidation of SO2 to So3 in contact process for the manufacture of H2 SO.4- Hemoglobin, a large molecule containing Fe24, acts as a catalyst in respiration of H2 SO.5- Pd is used as catalyst for hydrogenation of phenol to cyclohexanone.6- A mixture of Pt/Rh is used for oxidation of NH3 to NO in Oswald process for the

manufacture of H N O2.

INTERSTITIAL OR NON-STOICHIOMETRIC COMPOUNDS:

The transition elements from compounds of indefinite structure called interstitial or non-stoichiomery compounds. The non-stoichiometry is due to the variable oxidation state of d-block elements and also due to the defect in their solid structures which is due to the presence of small holes in crystal lattice of these elements. Small atoms such as H, B, C and N can reside within these holes without chemical reaction interstitial compounds include hydrides, nitrides and carbide. Alloys such as brass (Cu-Zn) bronze duralumin (Al Cu-Mg-Ni) are the examples of interstitial compounds.

COMPLEX COMPOUNDS FORMATION:

Transition elements form co-ordination compounds, which are called compounds or complexes A complex is a central ion linked to other atoms ion or molecules, which are called Ligands. If ligands are easily removed the complex as a said to be unstable and if they are difficult to remove, the complex is stable. Unlike s and p-block elements, transition elements have small, highly charged ions and vacant d-orbital of suitable energy to accept lone pairs of electrons donated by other group or ligands: These vacant d-orbital accept lone electron pairs from atoms, lons or molecules, called ligands, to from complexes. The bonding between the ligands and the transition metals ion can either be predominantly electrostatic or predominantly covalent or in many xases intermediate between the two extremes.For example:

Ferro cyanide {Fr(CN6}4 ion, Which is a complex ion containing six cyanide (CN) ions, Cash donating their lone electron pair to the central ferrous ion (Fe) forming an octahedral complex compounds.

TRANSITION METAL COMPLEXES:

A compounds containing the complex ion or molecule in which the central metal atom ion is surrounded by a number of oppositely charged ions or neutral molecules, called ligands. Is know as co-ordinate compound or complex. The ligands are law is bases i.e electrons pair donors attached to the metal atom in a complex. In these compounds, the central atom is always a transition elements

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and the number of ligands attached to it is called its Co-ordination number. It may also defined as the numbers of bonds the metal from ligands.For example:

Diammine curprous ion {Cu(NH3)2}in which central atom is cuprous ion (Cu) and the ligand is ammonia (NH3) which are two in number, therefore co-ordination number of this complex is two Co-ordination group or ligands (generally called lewis bases) are sub-divided into two main group.+

MONO OR UNIDATE LIGANDS (Meaning toothed ligands)

It contains only one co-ordinationating group. For example: H2O, CN, NO2 and halides.

POLY OR MULTIDENTATE:

It contain two or more electron-pair donor atoms in a molecule or an ion i.e it can from bonds through two or more atoms of its molecule, for example: (BIDENATATE) The ligands that can form two bonds with its atom or that contains two donor electron pairs. Such as:

H2N CH2 CH2-NH2 and COO oxatate ion C2O4(Ethylene diammine)_ COO

TRIDENTATE:

It contains three donor of electron pair. Such as: H2N-CH2-CH2-NH-CH2-CH2-NH2 (Dithylene thiamine )

CHELATING AGENT:

The poly or multidentates are also called chelating agent they from quit stable complex. When chelating agent forms a ring structure on co-ordination with a central metal atom, is called chelae compound which means crabs claw the term chelae is derived from Greek word chelae means claw for ample nickel dim ethyl glyoximate chalets are stable and highly colored compounds.

NOMENCLATURE OF CO-ORDINATION COMPOUNDS BY IUPAC SYSTEM:

International union of pure and applied chemistry (IUPAC) recommend following rules for naming the co-ordination compounds.

1- In simple ionic compounds (salts) the action is named first and then the anion. 2- In a complex whether anion action or neutral species, ligands are named first in alphabetical

order, and metal atom is named second the perefixes di-tri-tetra-etc(or prefixes bis-tris-tetrakis-pentakis-etc for ligands having Greek prefix) are used with the name of ligands when more than one ligands of the same of kind occurs with in the complex ion.

3- The name of the anion ligands are modified to endin o for example floure (F)-cholro (Cl) bromo (Br) iodo (!) cyno (CN) nitro (NO2) nitrato (NO3) hydroxo (OH2) amido (NH2) oxalate (C2O4) carbonate (CO3) Oxo (O2) and sulphato (sO4)

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4- The name of neutral legends usually remain unchanged there are however several important exception which are water ammonia and carbon monoxide water (H,O)is called aqua, ammonia and carbon monoxide (CO 32-)as carbonyl.

5- The charge of the central metal ion is indicated by a roman numeral in parenthesis (1,2,3,4,etc)Following the name of the metal, an oxidation state zero is indicated by (o) when the complex is either action or a neutral species. The central ion is written is its English named followed by the oxidation state (the charge number) in roman numerals in parenthesis e.g nickel (o), iron (2) copper (1) etc. when the complex ion is anionic the suffix-ate is added often to the stem of the Latin name for the metal (except mercury) e.g ferrate, stannate, aurate plum bate etc. the formal oxidation state is again show by roman numeral in parenthesis for example:

{Ag(NH3)2}Cl dimmine silver(1) chloride{Co(en)2BVr3}Cl dibromobis (ethylene daimmine) cob at 3) chloride{Co(en)3}NO3)3 Tries (ethylene daimmine) cobalt(3)nitrate{Co(H2O)6}SO4 Hex aqua cobalt (2) sulphate{Co(NH3)3(NO2)3} Tremunine trinitro cobalt (3){Co(NH3)4(H2O)Cl}Cl2 termuinine aqua chloro cobalt (3) chloride{Co(NH3)5 Cl}Cl2 pentaammine cobalt(3) chloride{Co(NH3)6 Cl3 Hex aqua chloro chromium (3) chloride{Co(NH3 Cl}Cl2 Tremunine chromium (3) chloride{Cr(H2O)5 NO3)3 Hex aqua chromium (3) nitrate{Cr (H2O)6}NO3)3 Hex aqua chromium (3) nitrate{Cr NH3)4CI3 ]CI Dichloro eraammine chromium (3)chloride

{CR (NH3) 6}CI3 Hexaaqua chromium (3)nitrate {Cu(NH3) 4} SO4 Teraammine copper (2) sulphate {CU(NH3)4}(OH)2 Teraammine dihydrooxo cuprate (2) [K2[Cu(CN)4] Potassium tetracyano cuprate (2) [K2[PICI6] Potassium hexachloro cuprate [K2[Co(NO2)6] Potassium hexanitro cobalte ( 2) [k2[Fe(CN)6} Potassium hexacyano ferrate (3) {K4{Fe (CN)6 ] Potassium hexacyano ferrate (2) [K4[Ni (CN)2 (OX)2} Potassium dicyano di oxalate nick elate (2) Na{Ai (OH)4} Sodium terahydrooxo aluminates (3) Na2{s N (OH)6} Sodium terahydrooxo slannate (4) Na3(Co(NO2)6} Sodium terahydrooxo cobaltite (3) NH4{Cr(NCS)4, (NH3)2} Ammonium terathiocyanato diammine ehromate (3) {Ni(CO)4} Teraearbouny nick elate (0) {Pt(N H3)4}{PtCl6} tetra mine platimmum (2) hexachord palatinate (5) Pt(NH4)2 Cl4 diammne tetrachloride plat mate Pt(H2O)2 Br4 diaqua tetrabromo plat mate Fe4{Fe(CN)6 Ferries hyxacyano fenate (2)

METALLURG OF COPPER:

OCCURRENCE:

Copper occurs both in free and combined state in combined state the chief ores are:

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1. Chalcopyrite or copper pyrite (CuFeS2)2. Chalcocite or copper glance (Cu2 S)3. Cuprites or red copper (Cu2O)4. Indigo copper (C u S)5. Malachite {CuCO3. Cu(OH)2} Bright green6. Azurite {2CuCO3 Cu(OH)3} deep blue7. Tanorine Cu2O8. Boranite Cu3FeS3

EXTRACTION OF COPPER (By Bessemer converter)

Copper is commonly extracted form supplied ores (chalcopyrite write) when contains about 6%cu.It is first crushed or pulverized, concentrated by froth floatation process and then roasted in a furnace with limited supply of air where the following ocher: Most sculpture dioxide (SO2) Iron oxidizes to ferrous oxide (FeO) Copper change to cuprous supplied (Cu2S) 2cuFeS2+4O2 ------- Cu2S+4FeO +3SO2

The roasted metal is then mixed with and (Sio2) to remove iron as ferrous silicate (FESIO3) FeO + SiO ------ FeSiO FeSiO3 Floats one the surface of molten matte and is removed as slag .The copper matte containing Cu2S with some FeS and silica is then oxidized in Bessemer converter by blowing air through it as shown in the figure FeS is oxidized to FeO and SO2and Cu2SO to Cu2O and SO2 as Follows : 2Fes +3O2---------2FeO +2SO2

2Cu2S +3O2--------2Cu2O+2SO2

Cu2Othus produced reacts with remaining Cu2Sto give metal lie copper. 2Cu2O +Cu2S ------- 6Cu + SO2

Copper thus produced is 98-99% pure and is called blister copper because as it solidifies some dissolved SO2 gas in metal escapes forming leisters or bubbles on its surface in blister copper Zn. As. Ag. Au Bi. Pb, SnFe and pt may also be present as impurities. Thus is refined or purified blister copper is further purified for to reasons:

1. Copper is used in making wires and cables for electrical conduction its conductivity is appreciably lowered by traces of impurity.

2. it contains traces of silver gold and platinum which from a value able mud in electrolytic cell make the process economically feasible.

REFINIG OF COPPER FROM BLASTER COPPER (BY ELECTROLYSIS):

Copper is refined by electrolysis in which block of blaster copper are as anode and thin sheets of pure copper as cathode, these sheets are coated with graphite in order to remove easily the despised copper on them 15% CuSO4Solution acidified with little 65% H2SO4is used as electrolyte and a current of 1.3 volt is is used for electrolysis which helps to deposited only copper on the cathode leaving impurities (such as .Zn . Ni. Co. Ag. Au. Pt. etc.) fall to the bottom of the cell as asludge or anode mud . The cell reaction occur as following: Cu(blister) --------- Cu2+ 2e (At anode ) Cu2+ +2e-------- Cu (pure|) (At cathode) Copper thus obtained is 99.96to 99.9% pure

CHEMISTRY OF SILVER NITRATE (AGNO3) (LUNAR CAUSTIC):

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PREPATION:

Silver nitrate or lunar caustic is prepared when silver metal is dissolved in cold or hot diluted HNO3 and resulting silver nitrate solution is evaporated and allowed to crystallize 2Ag + 4HNO3 ----------- 2AgNO+2H2O As such transparent large rhombic crystals or stick of AgNO3 are formed.


AgNO3is readily solube in water it is also soluble in organic sol-vents such as C2H5Opyridine etc. it is called lunar caustic because it corrodes the skin and produces black spots on it its melting point is 2I20 C and decomposes at 4500 C giving NO2 and O2gases and leaving Ag metal. 2AgNO3 ------------ 4500C Ag + 2NO2 +O


RECTION WITH Noah:

AgNO3When related with Noah first forms very unstable silver hydroxide (AgOH) which decomposes to stable blackish –brown silver oxide (Ag2 O ). AgNO3 + Noah ---------AgOH + NaNO3

2AgOH --------- Ag2O + H2O

REACTION WITH AMMONIA:

AgNO3 When related with ammonia in water forms precipitates of silver oxide. These precipitates dissolve in excess solution of ammonia forming deep-blue complex diammine silver (1) nitrate as follows:

AgNO3 +2NH3 ----------- [Ag(NH3|2 ]NO3 [diammine silver (1)nitrate]

USER OF SILVER NITRATE:

1. It is used as an important laboratory reagent. Especially lore the detection and estimation of halide ions. It gives white, light yellow and yellow precipitate of C; Br and I ions respectively.

2. It is widely used in photography and medicines. 3. 3. it produces black spots when comes in contact with or game matter such as

skin ,cellulose paper etc. 4. It is used industrially to produce other silver compound particularly silver halides

which are used and photography.5. It is used as indelible ink for making lien.

COPPER SULPHATE (CUSO4.5H2O) (NEELA THOTA):

INTRODUCTION:

It is able colored crystalline solid called blue vitriol or blue stone and is commonly know as neela thotha:

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PREPATION:

1. It is industrial, by reacting metallic copper with dilute H2SO4 in the presence of air 2Cu+2H2SO+O 2 CuSO4+2H2O2. By dissolving copper oxide (CuO) OR COPPER CARBONATE (cUco3) in dilute H2SO4

and then heating the solution to obtain saturated solution which on further heating crystallize out as large blue triclinic crystals. CuO+H2O4 CuSO4+H2O CuCO3+H2SO4 CuSO4+CO2+H2O


It is very poisonous substance. It is readilty soluble in water but in insoluble in alcohol and can be precipitated from its aqueous solution by addition of C2 H5 OH


HEATING:

Crystalline CuSo4 5H2O is blue in color which loses four of its molecules on heating at about 100c the fifth molecule is also on heating at about 250C and slowly changes in to colorless powered form or anhydrous CuSO4 the anhydrous salt decomposes into CuO and SO3 on strong heating at about 736C.

CuSO4 4H2O----------CuSO4+5H2O Blue (hydrated) --------- color (anhydrous) CuSO2---------------- CuO+SO3

REACTION WITH POTASSIUM IODIDE:

It reacts with ki solution liberating iodine. 2CuSO2+?4Ki Cu2I2+2KSO4+I2

REACTION WITH AQUEOUS AMMONIA:

It reacts with aqueous ammonia solution forming place blue gelatinous precipitate of cupric hydroxide Cu (Oh) which readily dissolves in excess solution forming deep blue complex cupric tetra mine sulphate as following:

CuSO4+2NH3+2H2O SMALL Cu (OH)2 +(NH4)2 SO4

CuSO4+4NH3 EXCESS Cu (NH3)4 SO4 Curpic tetrammine sulphate)

REACTION WITH ALKALIS:

CuSO4 reacts with alkali to produce blue colored ppt of cupric hydroxide. CuSO4+2KOH----------------Cu (OH)2+K2SO4

REACTION WITH HCL:

It reacts with HCL to produce cupric chloride.

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CuSO4+2HCL---------CuCL2+H2SO4

USES OF CuSO4:

It is use in copper plating in electric in cells, in making green pigments, containing copper ebonite as modern dying dyes and with milk of lime to kill fungus. It is used as timber preservative it is used as calico in printing trade.

POTASSIUM CHROMATE (K2 CrO4)

PREPATION:

It is prepared by strong heating a mixture of finely powdered mineral chromate or ironstone (ferrous chromate) and potassium carbonate or potassium hydroxide.

4FeO Cr2O3 +K2CO3+7O2 8K2 CrO4+2Fe2O3+8CO2

4Fe Cr2O4 +16KOH+7O2 8K2 CrO4+2FeO3+8H2OOxidation is fasten with a mixture of potassium carbonate and potassium nitrate or chlorate.

2FeCr2O4+4K2CO3+7 KNO3 4K2 CrO4+Fe2O3+7K NO2+4 CO2

6FeCr2O4+ 12K2CO+ 7KClO3 12K2CrO4+3Fe2O3+7KCl+12CO2

It is prepared by boiling chromium oxide with potassium hydroxide and bromine water. Cr2O3+10KOH+3Br2--------------2K2CrO4+6KB+5H2OIT is prepared by heating a mixture of K2Cr2O2 and KOH. K2Cr2O7+2KOH----------2KCrO4+H2O

PROPERTIES:

It is lemon-yellow crystalline solid substance. It melts at 968.30 it is isomophous with K2SO 4. It is very soluble in water and gives a yellow colored alkaline, which changes to orange-red on addition of H2SO4 due to formation of dichromate ion.

2CrO4+2H*------------------CrO2+H2O (Chromate ion) yellow (dichromate ion) orange-redPotassium chromate converts to dichromate in the presence of carbon dioxide. 2K2Cr4+CO2------------------K2Cr2+K2CO3

If forms precipitate of lead chromate with lead ion and barium chromate with barium ion. CrO4+Pb2*--------------PbCrO4

CrO4+Ba2*--------------BaCrO4

USES:

K2CrO4 is used a laboratory reagent, especially as an oxidizing agent and indicator. It is used to prevent the corrosion. It is used for the preparation of pigment, such as chromate yellow and chrome red which is used for painting letterboxes.

POTASSIUM DISCHROMATE (K2CRO4) (SURKH KAHI):

PREPERTION:

1. It is prepared by adding a requisite amount of H2SO4 in sutured solution of potassium chromate they crystallizes on cooling in orange-red triclinic crystals.

2K2CrO2H2SO ------------- K2CrO7+H2O

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2. It is prepared by adding hot cone solution of potassium chloride and sodium dichromate and cooling the resulting solution.

Na2CrO2O7+ 2KCI -------------- 2NaCI+ K2Cr2O7

PHYSICAL PROPERTIS:

It is orange-red crystalline solid. It melts at 3960. It is moderately soluble in cold water and easily soluble in hot water giving an orange color in solution. The color changes to yellow on addition of an alkali due to the formation of chromate.

K2Cr2O7+2KOH--------------2K2CrO4+H2O


REACTION WITH H2SO4:

It gives red needle-like crystal chromate oxide (CrO3) when its cone solution reacts with cone H2SO4

K2Cr2O7+2KOH----------------2K2CrO3+2KHSO4+H2O

REACTIONWITH KCL (Chromyl Chloride Test):

It gives deep-red needle-like crystals of chromic oxide (CrO2Cl2) When reacted with solid KCL or Na Cl in the presence of cone. H2SO4

K2Cr2O7+4KCl+6H2SO4-----------2CrO2Cl2+6KHSO4+3H2O K2Cr2O7+4NaCl+6H2SO4----------2CrO2Cl2+2KHSO4+4NaHSO4+3H2O

AS OXIDIZING AGENT:

It acts as a strong oxidizing agent in the present of H2SO4 and oxidizes ferrous (Fe2*) salt to ferric salts (Fe3*

6FsO4+K2Cr2O7+7H2SO4---------3Fe2 (So4) +K2SO4+Cr2 (So4) + 7H2OIt also liberates iodine from potassium iodide in the presence of H2SO4. 6Kl+K2Cr2O7+7H2SO4-------------4K2SO4+Cr2 (SO4) +7H2O

USES:

It is as powerful oxidizing in the volume analysis of ferrous ion it is used for the preparation of chromium compounds such as chrome alum chrome red which are used as pigment it is used the preparation of acetaldehyde and ethyl alcohol. It is used industrially in the tanning of leather in the preparation of electrolyte used in chrome plating, and as a source of pure chromium.

POTASSIUM PERMANGANATE (KMNO4) (Pinki or lal dawa)

PREPATION ON LARGE SCALE:

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It is prepared on large scale from manganese dioxide (MnO2) by fusing it with potassium hydroxide in an iron dish in the presence of plentiful air or an oxidizing agent such as potassium nitrate or produce green colored potassium magnet (K2MnO4) on evaporation in a vacuum.

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chemistry xii 1-5 inorganic

Documents

properties of elements

classification of elements

group of elements

elements triad

noble elements

known elements

middle elements

dissimilar elements