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METALLURGY-II- 4Hrs X1.5 =6 marks

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Q 2.Name the process used for desilverisationo ea pr une ar

300 1300

lead molteninsilverof Conc.cmolten Zininsilverof Conc.

efficient-co partition===

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[March 08 &09] (3Marks)

Parkes process is based on the following ac s r nc p e :

*Argentiferrous lead contains up to 2% silver o en z nc mo en ea can ecome

immiscible liquid mixture ,

300 times more soluble in the molten Zn layer com ared to that of molten lead* Zn Ag alloy solidifies more readily compared to that of molten lead ,when cooled.

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Alexander ParkesDate of birth : 1831 12 29Date of death : 1890 06 29Birthplace : Birmingham, England

Credited as : Engineer metallurgist, invented the earliest form of lastic * The son of a brass lock manufacturer, Parkes was born on December 29, 1831, in Birmingham, England .* Parkes held 66 patents on processes and products related to electro plating and plastic development

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Process: Argentiferrous lead is melted to 800 oC.It is mixed with molten zinc

As

silver

300

times

more

soluble

in

molten

zinc ,most of the Ag moves in to the Zn ayer.

On

cooling

,the

upper

Zn

Ag

alloy

solidifies

rs . s s mme o . The Zn Ag alloy is distilled in retort to

separa e

z nc

rom

s ver The traces of lead impurity is removed by

upe a on7


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ng am agrams Ellingham diagrams are plots of change in

temperature for various reactions like the

elements

oxides obtained by plotting the standard free ener chan e v/s Tem erature for the oxidation process involving one mole of oxygen at various temperatures.

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ng am agrams

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The graphs for the formation of metal oxides .

increases with temperature The sudden chan e in the slo e of the ra hs

indicate M.P & B.P For

oxides

of

Ag

and

Hg

the

std.free energy

temperatures4A +O 2A O2Hg +O2 2HgO

The metal oxides placed below are stable

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The metal of metal oxide placed below can

diagram The line for the formation of CO is arallel to

temperature axis as change in free energy

remains

constant. (S)

2(g) 2(g) The graph for the formation of CO has negative

slo e as entro increases and free ener decreases

2C (S)+ O2(g) 2 CO(g)

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Q.5 With the help of the Ellinghams diagram,explain why silver oxide can be thermodynamically decomposed at relatively lower temperature [july 2009] (2 Marks)

Chan e in std.free

energy

change v/sTemperature curves

Ag & Hg crosses zero

line

&

their

change

in

s . ree energy become +ve even at lower tem erature

So these oxides become unstable & readily decompose on heating

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Q.6With the help of the Ellinghams diagram, explain

manufacture of chromium from chromic oxide. [April 2007] (2Mark)

Std. Change in free energy va ue or e orma on o Al2O3 is always less than that

2 3. Al2O3 is more stable

Cr2O3(Chromic oxide)

Goldschmidt aluminothermic process

Cr2O

3+2Al Al

2O

3 +2Cr

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Q.7 With the help of Ellingham diagram,explain why

carbon monoxide acts as reducin a ent in the production of cast iron from Haematite.(2Mark)

, .in free energy for the formation of Fe O is more than that of

formation

of

CO2 form

. ere ore s better reducing agent for Fe O below 710 0C.

Fe2O3 +3CO 2Fe +3CO2

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Above 710 0C, the std

.

value for the formation of Fe O is more than

that

of

CO

formation

from Carbon(Coke) Hence above 710 0 C,

coke (carbon

)

is

better

reducing agent for Fe2O3.

Fe2 3 +3C

Fe

+3CO

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Q 8.Explain the chemical reactions that occurduring the extraction of iron from haematite

ore by smelting in a blast furnace (3 Marks)

Q 9 Explain the chemical reactions that occur during the extraction of cast iron At i Zone o combustion ii zone of reduction iii)zone of slag formation of blast funace.

OR (3 Marks)Q 10 Draw a neat labelled diagram of blast

furnace used in the extraction of cast iron. Give

e c em ca reac ons a a e p ace n edifferent zones of the furnace. [April-2007]3Marks

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Haematite Fe2O3 Magnetite Fe3O4 Limonite 2Fe O .3H O Siderite FeCO3

2

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M ll r f Ir n F

I. Concentration of Haematite

with a current of water

calcination Vo at e mpur t es are remove . If there is any traces FeO, it is oxidised to

Fe2O3. The ore become orous .

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A mixture of haematite Ore +lime stone+ Coke (8:1:4) is introduced in to a tall cylindrical blast urnace y means o cup ou e cone a e op

of the furnace.

Boshes

Hot air is blasted into the furnace just below the boshes using tuyers

I. Zone of combustion (1500 0 C)

C

(S)+

O2(g) CO2(g)+406kJDue to this exothermic reaction , the temperature

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ra ses o a e com us on zone .


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As the CO2 raises up the furnace,coke

combines

with

CO2 to

form

CO

CO + C 2CO 163kJ This reaction is endothermic. Therefore the

bottom(1500 0C) towards the top(400 0C)

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0 0

At about 600 0C, Fe2O3 is reduced by CO to give

Fe2O3 +3CO

2Fe

+3CO2

furnace called pig iron or cast iron

III.Zone of sla formation: at 900 0CCaCO3 CaO + CO2

+

(flux) (gangue) (slag)

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Q.12 What is the function of lime stone & coke in the smelting of haematite ? 1Mark

acts as flux 3

2

CaO +

SiO2 CaSiO3(flux) (gangue) (slag)

Coke roduces CO which acts as reducin

agent Fe2O3 +3CO 2Fe +3CO2

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. of combustion in the blast furnace july 2009

Coke

burns

with

air

to

produce

carbon

dioxide C (S)+ O2(g) CO2(g)+406kJ

temperature raises to 1500 0C at the

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IndustriallyI C dmportant Compounds

4hrs X 1.5 =hrs X 1.5

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. Q.14 .With a neat labelled digram explain the

manu acture o caustic soda usin Nelson cell (July 07 &2011)

Principle:a a +

H2O H+ + OH

Na +, Cl , H+ and OH

During electrolysis, only H + ion reduced to H2 at

cathode .Similarly only Cl is oxidized to Cl2 at anode

e so ut on ecome r c er n a ons27


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At Cathode;(Reduction) 2H+ +2e H2 At ano e : Oxi ation 2C 2e + C

2 The solution becomes richer in NaOH.It

collects in the catch basin at the bottom The

steam

is

circulated

to kee the electrolyte warm & to keep the pores clean and clear Purification: The 98% pure NaOH is further

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Uses o NaOH: , In Baeyers process Re ining o petro eum & vegeta e oi

In

the

form

of

sodalime (NaOH +

CaO)

used

as decarboxylating agent In mercerizin cotton in textile industr in volumetric analysis

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Manufacture of ammonia By Habers processQ.How is ammonia manufactured by Habers process?

Habers process involves the direct com nat on o 2 2

N2+ 3H2 2NH3 + Heat According to Le Chateliers principle ,The

followin

favorable

conditions

ive

better

ield

of ammonia; i)Finely divided Fe catalystii a romoter like Mo or K O or Al O .iii)a moderate temperature of 773K (500 0C)

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It

is

thought

that

two

in

five

people

owe

their existence to the discoveries made by one brilliant chemist. However despite his incredible

discovery

many

people

still

call

Fritz

Haber a

mur erer. It has been suggested that without this process,

Germany

would

not

have

fought

the

war,

or

would have had to surrender years earlier

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Manufacture of ammonia

By Ha er s process

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Step III: Cooling The gaseous mixture is passed through

. 3Step IV: Recycling The unreacted gases are collected & recycled NH as

is

dried

over

CaO to

et li uor ammonia

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In the manufacture of fertrilisers like ,

As refrigerant due to its high heat of

In the manufacture of HNO3 by Ostwalds

As a non aqueous solvent

2 3

process

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Manufacture of H2SO4 by Contact process

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St II P ifi ti f G


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Step II; Purification of Gasesx ure

o

2

2 s

pur e

y

pass ng

through a series of Chambers;

1)Dust chamber: Steam

is

passed.

Steam

condenses on the dust articles which settle at the bottom

passing through cooling pipes

3)Scrubber: Water

is

sprayed

from

the

top

of the tower. Water soluble im urities are removed.

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4) Cottrell precipitator: Electrically charged colloidal particles are removed

spraying Con.H 2SO4. 6)Arsenic purifier: As2O3 impurity is

removed

b

usin

Fe OH t. 7)Tyndall box: Pure & dry gas is passed

presence of colloidal impurities

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Step III; Oxidation of SO2 to SO3. 0

passed

in

to

the

converter. 2 5

catalyst & maintained at 500 0C. 2SO2(g)+O2(g) V2O5 or Pt 2SO3(g)+188

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SO3 gas is absorbed by using Con.H 2SO4

or Fuming sulphuric acid . SO3 + H2SO4 H2S2O7

(OLEUM)

O eum is care u y i ute wit ca cu ate amount of water to obtain 98% H2SO4.

H2S2O7 +

H2O

2H2SO4.

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Q17 N h l d i h C


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Q17.Name the catalyst used in the Contact

process

u y

mar

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St III:C v r i n N Cr t N Cr

Na2CrO4 is treated with calculated amount of . 2 4 Na 2Cr2O7

2Na 2CrO4 +H2SO4 Na2Cr2O7 +Na2SO4 + H2O

The less soluble Na2SO4 crystals are removed

.

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St IV:C v r i n N Cr t K Cr

treated

with

calculated

amount

of

KCl2 2 7 2 2 7

(Sod.dichromate) (pot.dichromate)

The solution is concentrated ,less soluble K2Cr2O7 separates out. The crystals are

removed

by

filtration.

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As

primary

standard

in

volumetric

analysis Use to c ean g ass apparatus in t e orm o

Chromic acid Used in Chromyl test In Chrome tannin of leather As mordant in dyeing industry

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Chemical properties of H SO


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Chemical properties of H2SO4e y ra on

proper y: Q19.How does Conc.H 2SO4 react with oxalic acid

.

H2C2O4 +Conc.H2SO4 CO

+

CO2+[H2SO4.H2O]

. 2 4 2 4. 2

Oxidation propety:

. 2 4 reaction, H 2SO4 H2O + SO2 +(O)

2

2

c)H2S to S d)C to CO2 e)S to SO2 etc .

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Q 20 H S cannot be dried with con H SO


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Q 20.H 2S cannot be dried with con.H 2SO4.ve reason u y

Conc.H2SO4 oxidizes H2S to S H2S +ConH2SO4 SO2 +2H2O +S

Q. What happens when con.H 2SO4 reacts with

PCl 5? (

March11)

2mark

H2SO4 + PCl5 SO3H Cl + POCl3 + HClchlorosul honic acid

H2SO4 + 2PCl5 SO2Cl2 + 2POCl3 +2HCl

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Q 22 Explain Chromyl chloride reaction ( june 2011)


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Q 22. Explain Chromyl chloride reaction ( june 2011)

mar

W en a mixture o potassium ic romatecrystals and a water soluble chloride is heated with Con.sulphuric acid , red vapoursof chromyl chloride is evolved

K2Cr2O7 + 4KCl + Con.6H 2SO46KHSO + 2CrO Cl +3H O

(chromyl chloride)

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Q Write the molecular formula of Chromyl


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Q. Write the molecular formula of Chromyl

c or e.

une

mar

2CrO2Cl

2

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[email protected], 62


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Q23.Mention two reasons for the formation of


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(2m)

Hig c arge size ratio i.e ig po arization

power

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Q 24.Why are transition elements &their


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Q y

compoun s goo cata yst xp a n (2m)

Presence o vacant or ita s using w ic unstable intermediate compounds can be orme w c ecompose g v ng pro ucts

c)In

their

finely divided form

they

can

produce

lar e sur ace area for adsor tion

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Q 25.Which among Cu+ &Cu+2 salts is


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Q g

co oure 1m 2+

unpaired electron2+ 9 0 .

E.C of Cu+ :[Ar]3d 10 4s 0 No unpaired electron

4 2

4

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Q 26.Among Sc3+(Z=21) &Cr3+(Z=24),which is


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g ( ) ( )

co oure .

y (2m)

3+ 0.

In

Sc3+,there

are

no unpaired electron.

E.C of Cr3+ is [Ar]3d 3 4s 0

There are three unpaired electrons in 3d orbitals. Hence it should be paramagnetic &

coloured

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Q 28.Write the electronic configuration of 3d series of + 3+


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+ 3+.

are colourless ii)Zn 2+ ions are diamagnetic a)E.C of 3d series of elements

[Ar]3d (1 10)4s (1 2)

i) E.C of Cu+ :[Ar]3d 10 4s 03+ 0 0.

There are no unpaired electrons in both of them.

ere ore ey are colorless & diamagnetic .

ii) E.C of Zn2+ :[Ar]3d 10 4s 0

Zn2+

also

has

no unpaired

electron. It is also diama netic and colorless

69

Q 29.Name the transition metal in 3d series


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w c

s ows

max mum

ox at on

state (1m)

maximum oxidation state of +7

permanganate solution

4

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Wh F 3+ i n i m r ta l than F 2+i n?


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.Wh F i n i m r ta l than F i n?

OR Sma er t e size ig er t e sta i ity

OR Higher the oxidation state ,more is the

stabilit

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TH NK YOUH NK YOU


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TH NK YOUH NK YOU

WISH YOU GOOD LUCK

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