Lesson 2 & 3 Rates of Chemical Reactions

NATIONAL 5 CHEMISTRY

UNI1 1 CHEMICAL CHANGES AND STRUCTURE Contents Page SUB-TOPICS

RATES OF REACTION ATOMIC STRUCTURE AND BONDING RELATED TO PROPERTIES OF MATERIALS FORMULAE AND REACTION QUANTITIES ACIDS AND BASES

RATES OF REACTION

REVISION OF FACTORS THAT SPEED UP A REACTION

Learning intentions Describe using collision theory how rates of reaction are affected by temperature, surface area and concentration.Predict the effect any change to one of the factors above would have before experimental observation. Evaluate from experiment if the factors from above have indeed changed the speed of a chemical reaction in the manner described by collision theory. Reminder from S3:What are the signs of a chemical reaction?

Signs of a chemical reaction are:1. Change in colour (for example silver to reddish brown when iron rusts)2. Change in temperature or energy, such as the production (exothermic) or loss (endothermic) of heat 3. Light, heat or sound is given off.4. Change of form (for example, burning paper).5. Formation of gases often appearing as bubbles. 6. Formation of precipitate (insoluble solid usually from two solutions when mixed)

Important Point to note

In order for chemists to monitor the rate of a reaction we must observe a CHANGE in response to a chemical reaction occurring against TIME.

REACTANTS PRODUCTS e.g. magnesium + hydrochloric acid magnesium chloride + water + hydrogen

Factors Affecting the Rate of ReactionFor chemical reactions to take place, the reactant particles must meet and collide with each other.

Not all collisions result in a chemical reaction taking place - the collisions must take place with sufficient energy to break any bonds within the reactants.

This energy, used to start the reactions is called activation energy. Rates of ReactionEffect of concentrationIntroduction to collision theory Effect of temperature Contents of lesson Effect of surface area12 Rates of reactionsThe speed of different chemical reactions varies hugely. Some reactions are very fast and others are very slow.fastvery fastvery slowfastslowBurning magnesium fireworkschemical weathering of rockssodium and waterrotting fruitReactionRate13Reactions occur when particles of reactants collide with enough energy to react (activation energy). Reactants state i.e. solid, liquid or gas will have to be taken into account when thinking about [collision theory]. Collision theory Rates of ReactionEffect of concentrationIntroduction to collision theory Effect of temperatureEffect of surface area Contents15Temperature and rate of reaction video

Video The effect of temperature on collisionsHow does temperature affect the rate of particle collision?

17Temperature and particle collisions

18Boardworks GCSE Additional Science: Chemistry Rates of ReactionTeacher notesThis simulation illustrates how increasing the temperature increases the number of collisions between particles.Rates of ReactionEffect of concentrationIntroduction to collision theory Effect of temperatureEffect of surface area Contents19

What is concentration?

When a solute (e.g. coffee, salt etc.) is dissolved in a solvent (e.g. water, alcohol etc.) and the resultant mixture is a solution Solute Solvent After they mix it is a solutionConcentration has the units (mols/l) which is referring to the amount of solute per unit volume of water we will look at this specifically much later in the topic.

For example these examples all have the same volume of solvent but the amount of solute added is changed

Increasing concentration22Concentration and reaction rate

Dilute hydrogen peroxide solutionConcentrated hydrogen peroxide solutionAdd more solute (hydrogen peroxide) to the same volume

Video ConcentrationReactions in solution involve dissolved particles. The more crowded (concentrated) the solution, the faster the reaction.Higher concentration more particles more collisions faster reactionRates of ReactionEffect of concentrationIntroduction to collision theory Effect of temperatureEffect of surface area Contents25

Surface area and reaction rate videoIncreased surface area 5g Marble powder 20 ml 0.1 mol HCl 5g Marble chips medium size20 ml 0.1 mol HCl 5g Marble lumps large size20 ml 0.1 mol HCl

Video 26Surface areaMolecules collide with the surface of the solidExtra surface for molecules to collide with. Reactions of solids can only take place at the surface of the solid. If we break a solid into smaller pieces we get a larger surface area and a faster reaction.Smaller particles larger surface area more collisions faster reactionIf we grind up a solid to a powder we massively increase the surface area.We therefore massively increase the rate of any reaction Very fastSlowSurface areaSummary of the factors which can affect the rate of a reaction are;-Particle size/surface areaConcentration of reactantsTemperature of reactantsParticle Size/Surface AreaDecreasing the particle size of a solid in a reaction, increases the surface area available for contact between the reactants.

Particle size is halvedNew surfaces available for contactIf the surface area available for contact is increased, the rate of collisions will increase and hence the reaction rate will increase.ConcentrationTo increase the concentration of a solution you increase the amount of solute dissolved in the solvent. This means that the number of particles in solution increases. More particles means more collisions which leads to an increase in the rate of reaction.TemperatureAs you increase the temperature of something you give it more energy making the particles move faster, so they collide more frequently. This increases the number of successful collisions and hence the reaction rate.

Also, as the particles are now moving faster, the collisions between them have more kinetic energy. This means that more reactions have the required activation energy.

Particles and rates of reaction copy and complete 33NATIONAL 5 CHEMISTRYCHEMICAL CHANGES AND STRUCTURE

LESSON 2

MEASURING AND CALCULATING THE RATE OF REACTION

True or false?35Calculating the Rate of ReactionThe rate of reaction can be calculated by measuring the :1. Time taken for the reaction2. One other variable (something that changes) e.g.Volume (cm3)Mass (g)Concentration (moles per litre = moll-1)andRate =Change (in variable) Time taken

Example 1Use the graph below to calculate the rate of reaction for the first 20 seconds.

Average rate = (change) / time

20 cm3/ 20 s

1 cm3 S-1Example 2Use the graph below to calculate the rate of reaction between 5.2 and 10.8 seconds.

Average rate = (change) / time 0.4 - 0.2/ (10.8 - 5.2)0.2 mol l-1/ 5.6 s

0.036 mol l-1 s-1Rates and GraphsThese show the increasing amount of product or the decreasing amount of reactant.Amount of productTimeAmount of reactantTimeSteep gradient Fast reactionShallow gradient Slow reactionSteep gradient Fast reactionShallow gradient Slow reactionRate graphs and reactant concentrationsAmount of productTimereactantsproductReactant Concentration fallsRate of Reaction fallsAll productAll reactantMix of reactantAnd productGradient of graph decreasesCalcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water CaCO3 + HCL CaCl2 + CO2 + H2OTime (s)Decrease in mass (g)Concentration of CO20-4.00301.252.86602.922.25902.401.821203.761.491503.061.221803.320.982103.520.802403.680.652703.810.543003.920.443604.110.274204.230.154804.300.095404.350.046004.350.04Time (s)Volume of CO2 (cm3)003060609090130120142150154180162210171240173270174300177360180420195480200540200600200Activity 1 plot either of these graphs on graph paper and work out the average rate for the first 120 seconds and then between 300 600 seconds

Rate and TimeFor some reactions, a colour change will indicate the end of the reaction.The only measurement carried out during this type of experiment is time. Therefore the rate equation is slightly changed from:Rate =Change (in variable) Time taken

No other variable measuredRate= 1Time takenUnits =per second (s-1)To:Concentration of sodium thiosulphate and the time taken for the cross to disappear

Concentration of Potassium Iodide (KI) Mol/l Time (S)Rate (1/t) S-11.0230.8290.6390.4600.2111Activity 2 - Plot a Time vs Rate Graph for this reaction and identify the relationship between concentration and rate of reaction 0.04350.03450.0270.020.009Video Rate = (1/t) S-1Concentration of sodium thiosulphate (mol/l) Q) How long did it take for the cross to be obscured when the concentration of sodium thiosulphate was 0.7 mol / l?

A) Rate = 1/t so we must rearrange the equation to Time = 1/rate and obtain the rate from the graph 0.7 mol l = 0.032 S-1 ; Time = 1/0.032 31.25 seconds ATOMIC STRUCTURE AND BONDING RELATED TO PROPERTIES OF MATERIALS

Atoms and the Periodic Table.We can classify (arrange) elements in different ways:-naturally occurring/made by scientistssolid/liquid/gasmetal/non-metal

The Periodic Table of the Elements.

The Periodic Table lists the chemical elements in increasing atomic number.The Periodic Table arranges elements with similar chemical properties in groups (vertical columns).All the elements in a group have similar chemical properties as they have the same number of outer electrons.The Periodic Table of the elements is a useful way of classifying the elements. A vertical column of elements in the periodic table is called a group.The elements in the same group of the periodic table havesimilar chemical properties.The noble gases are a group of veryunreactive elements.

Groups of elements have names: Group 1 -

Between groups 2 and 3 -

Group 7 -

Group 0 -

the alkali metalsthe transition metalsthe halogensthe noble gasesAtomic Structure Electron configurationSummary activities Isotopes Introducing atomsAtomic number and mass number Contents 50 Discovery of atomic structure

51 Atoms the building blocksAll substances are made from very tiny particles called atoms.John Dalton had ideas about the existence of atoms about 200 years ago but only relatively recently have special microscopes (called electron microscopes) been invented that can see atoms.The yellow blobs in this image are individual gold atoms, as seen through an electron microscope.

52AcknowledgmentThe image is a false-colour high-resolution transmission electron micrograph (HREM) of the atomic lattice of a thin gold crystal. Magnified 16 million times at 35mm size, each yellow blob represents an individual gold atom. The micrograph has been enhanced by optical image- processing techniques. The centre to centre spacing of the atoms is 2.04 angstroms (0. 204 nanometres); this represents the practical limit of resolution of the modern electron microscope.

Credit: Graham J Hills/Science Photo Library

Elements different types of atomElements are the simplest substances. There are about 100 different elements.

Each element is made up of just one particular type of atom, which is different to the atoms in any other element.Copper is an element made up of copper atoms only.Carbon is an element made up ofcarbon atoms only.

53 How small is an atom?Atoms are very small they are about 0.00000001 cm wide.NX3,000,000,000

If a football was enlarged by the same amount it would stretch from the UK to the USA!

To make an atom the size of a football it would have to be enlarged by about 3,000,000,000 times.54 The Amazing Atomic Zoom

55 Inside an atomWhere are the electrons and nucleus found in an atom?

56Atomic Structure Electron configurationSummary activities Isotopes Introducing atomsAtomic number and mass number Contents57 Even smaller particlesFor some time, people thought that atoms were the smallest particles and could not be broken into anything smaller.protonneutronelectronScientists now know that atoms are actually made from even smaller subatomic particles. There are three types:58 Where are subatomic particles found?Protons, neutrons and electrons are NOT evenly distributed in an atom.The electrons are spread out around the edge of the atom. They orbit the nucleus in layers called shells.The protons and neutrons exist in a dense core at the centre of the atom. This is called the nucleus.59 The atom: check it out!Draw a labelled diagram of the atom showing the nucleus and labelling protons, neutrons and electrons.nucleusneutronprotonelectron60ParticleMassChargeprotonneutronelectron Properties of subatomic particlesThere are two properties of subatomic particles that are especially important:1. Mass2. Electrical chargeThe atoms of an element contain equal numbers of protons and electrons and so have no overall charge.11+10almost 0-161 How many protons?The atoms of any particular element always contain the same number of protons. For example:

The number of protons in an atom is known as its atomic numberor proton number.It is the smaller of the two numbers shown in most periodic tables.hydrogen atoms always contain 1 proton;carbon atoms always contain 6 protons;magnesium atoms always contain 12 protons,62 Whats the atomic number?What are the atomic numbers of these elements?11

sodium26

iron50

tin9

fluorine63 More about atomic numberEach element has a definite and fixed number of protons. If the number of protons changes, then the atom becomes a different element. Changes in the number of particles in the nucleus (protons or neutrons) is very rare. It only takes place in nuclear processes such as:radioactive decay;nuclear bombs;nuclear reactors.64AtomProtonsNeutrons Mass numberhydrogenlithiumaluminium Mass numberElectrons have a mass of almost zero, which means that the mass of each atom results almost entirely from the number of protons and neutrons in the nucleus.

The sum of the protons and neutrons in an atoms nucleus is the mass number. It is the larger of the two numbers shown in most periodic tables.10131341472765127 Whats the mass number?What is the mass number of these atoms?7359644Mass number = number of protons + number of neutronsAtomProtonsNeutrons Mass numberheliumcoppercobaltiodinegermanium22293527325374324166 How many neutrons?How many neutrons are there in these atoms?AtomMass numberAtomic number Number of neutronshelium42fluorine199strontium8838zirconium9140uranium238925114650102Number of neutrons = mass number - number of protons= mass number - atomic number67 Building a nucleus

68Atomic Structure Electron configurationSummary activities Isotopes Introducing atomsAtomic number and mass number Contents69AtomProtonsNeutrons Electronsheliumcopperiodine How many electrons?Atoms have no overall electrical charge and are neutral. This means atoms must have an equal number of protons and electrons.The number of electrons is therefore the same as the atomic number.Atomic number is defined as the number of protons rather than the number of electrons because atoms can lose or gain electrons but do not normally lose or gain protons.22229352953745370AtomProtonsNeutronsElectronsAtomicnumberMassnumberboronpotassiumchromiummercuryargon Calculating the number of electrons51918248051918248011394052201What are the missing numbers?561920242880121182271 How are electrons arranged?Electrons are not evenly spread but exist in layers called shells.3rd shell2nd shell1st shellThe arrangement of electrons in these shells is often called the electron configuration.72 How many electrons per shell?Each shell has a maximum number of electrons that it can hold. Electrons will fill the shells nearest the nucleus first.

3rd shell holdsa maximum of8 electrons2nd shell holdsa maximum of8 electrons1st shell holdsa maximum of2 electrons73

Calculating electron configurations74 Properties of the nucleus and electrons

75Thinly spread around the outsideof the atom.Very small and light.Negatively charged.Found orbiting the nucleus in layers called shells.Able to be lost or gained in chemical reactions. Summary: the atom so farThe nucleus is:Electrons are:Dense it contains nearly all the mass of the atom in a tiny space.Made up of protons and neutrons.Positively charged because of the protons.76Atomic Structure Electron configurationSummary activities Isotopes Introducing atomsAtomic number and mass number Contents77 What is an isotope?Elements consist of one type of atom, but sometimes these atoms can be slightly different.

mass number is differentatomic number is the sameAtoms that differ in this way are called isotopes.Although atoms of the same element always have the same number of protons, they may have different numbers of neutrons.78 Properties of isotopesThe isotopes of an element are virtually identical in their chemical reactions.The uncharged neutrons make no difference to chemical properties but do affect physical properties such as melting point and density.Natural samples of elements are often a mixture of isotopes.

This is because they have the same number of protons and the same number of electrons.79 Isotopes of carbonMost naturally-occurring carbon exists as carbon-12, about 1% is carbon-13 and a much smaller amount is carbon-14.

6 protons6 neutrons7 electrons6 protons6 neutrons8 electrons6 protons6 neutrons6 electrons80 Isotopes of hydrogenHydrogen-1 makes up the vast majority of the naturally-occurring element but two other isotopes exist.

hydrogen

deuteriumtritium

1 proton0 neutrons1 electron1 proton1 neutron1 electron1 proton2 neutrons1 electron81 Isotopes of chlorineAbout 75% of naturally-occurring chlorine is chlorine-35 and 25% is chlorine-37.

17 protons18 neutrons17 electrons17 protons20 neutrons17 electrons82

What are the particle numbers in each isotope?1088888oxygen-16oxygen-18protonsneutronselectrons Isotopes of oxygenAlmost all of naturally-occurring oxygen is oxygen-16 but about 0.2% is oxygen-18. 83 Isotopes and RAMMany elements are a mixture of isotopes. The RAM given in the periodic table takes account of this.For example, chlorine exists as two isotopes:chlorine-35 (75%) and chlorine-37 (25%). To calculate the RAM of a mixture of isotopes, multiply the percentage of each isotope by its atomic mass and add them together.= (0.75 x 35) + (0.25 x 37)= 26.25 + 9.25= 35.5RAM of chlorine = (75% x 35) + (25% x 37)

84 Calculating RAMBromine contains 50.5% bromine-79 and 49.5% bromine-81.

= (0.505 x 79) + (0.495 x 81)= 39.895 + 40.095= 79.99= 80(the RAM is usually rounded to the nearest whole number)RAM of bromine = (50.5% x 79) + (49.5% x 81)

What is the RAM of naturally-occurring bromine?85 Summarizing atomic structure

86 Atomic structure word check

87Atomic Structure Electron configurationSummary activities Isotopes Introducing atomsAtomic number and mass number Contents88 Glossary (part 1)atom The smallest particle that can exist on its own.

atomic number The number of protons in the nucleus of an element, also known as the proton number.

electron Negative particle that orbits the nucleus of an atom.

element Substance made up of only one type of atom.

isotopes Different atoms of the same element. Theyhave the same number of protons and electrons, but a different number of neutrons.89 Glossary (part 2)nucleus The dense positive centre of an atom, made up of protons and neutrons.

neutron A neutral particle, with a mass of 1. It is found in the nucleus of an atom.

mass number The number of protons and neutrons in an atom.

proton A positive particle, with a mass of 1. It is found in the nucleus of an atom.

relative atomic mass (RAM) The mass of an element compared to the mass of 112 of the mass of carbon-12.90 Anagrams

91 Atomic structure word search

92 Properties of subatomic particles

93 Multiple-choice quiz

94

Bonding, Structure and PropertiesProperties of SubstancesEverything around us is made from individual elements or compounds.

These can be classified as follows:Covalent compounds Always contain non-metals.e.g. CO2, NH3, PCl5

Ionic compounds-Contains metals and non-metals.-e.g. NaCl, MgO, CaCO3BondingAtoms take part in chemical reactions to achieve a full outer shell of electrons.

The molecules or compounds formed are held together by chemical bonds.

Chemical Bondsare invisible forces of attraction.

There are 3 main types:Covalent bonds (in covalent molecules)Ionic bonds (in all ionic compounds)Metallic bonds (in all metals)Compounds and MoleculesCovalent substances are made up of molecules.

Molecules contain 2 or more non-metal atoms held together by covalent bonds.E.g. chlorine molecule

ClClDiatomic Molecules Contain 2 atoms onlyCarbon monoxideHydrogen chlorideOxygenNitrogenHydrogenGroup 7 elements

Forming Covalent BondsCovalent Bond: Bond formed between two non-metal atoms by sharing a pair of electronsHydrogen Molecule:Hydrogen atom + hydrogen atom = hydrogen gasCovalent bond: the two atoms share a pair of electronsEach hydrogen atoms now has 2 electrons in its outer shell. Therefore the shell is now full.StarterFill in the table below:Element Symbol Atomic no.Protons Electrons Neutrons Mass NumberCalcium OxygenArgonNitrogen Covalent BondsThe diagram below shows how a molecule is held together by a covalent bond.e-e-A covalent bond is the force of attraction between the nuclei and the shared outer electrons.The only type of covalent bond that has an equal share of electrons between the two atoms is when the two atoms are of the same element. e.g. H2, O2, Cl2. These bonds are called pure covalent bonds.

All other covalent bonds are classed as polar covalent bonds.

Polar Covalent BondsThe diagram of the covalent bond showed the outer electrons being shared equally between the bonding atoms.

When covalent bonds are formed between two different types of atoms, the electrons that are shared between the atoms are not equally shared.

This is because some atoms attract electrons more strongly than others. This attraction is called electronegativity.

In a molecule of water the bonding electrons are pulled closer to the oxygen atom.OHHe-e-e-e-++-= delta- = slightly negative+ = slightly positiveBecause the negative electrons are closer to the oxygen it becomes slightly negative.Molecule: Group of atoms held together by covalent bonds.FHe-e-+-These types of bonds are known as POLAR COVALENT BONDS.Bonding DiagramsN.B. Only outer electrons are involved in bonding.

E.g. chlorine gas, Cl2ClClN.B. Outer electrons are grouped together in pairs.Ammonia (nitrogen hydride), NH3NHHHStarterWhat are covalent bonds?Why do molecules form covalent bonds?How is the covalent bond held together?What is a diatomic molecule?

Oxygen gas, O2This can also be drawn as O=OOORememberThe covalent bond is a result of two positive nuclei being held together by their common attraction for the shared pair of electrons. Shapes of MoleculesThe shape of a molecule is determined by the number of bonds.

There are 4 basic shapes:

Tetrahedral

Any molecule with the formula XY42. Pyramidal

Any molecule with the formula XY3

3. Angular

Any molecule with the formula XY2

4. PlanarH ClAny molecule with the formula XY

OHHStarterWhat are covalent bonds?Why do molecules form covalent bonds?How is the covalent bond held together?What is a diatomic molecule?Covalent CompoundsThere are two types of covalent compounds:

Discrete covalent moleculese.g. CO2, HF, CH4, N2

2. Covalent networkse.g. C, SiO2, CS2

1. Discrete covalent moleculesThese are substances made up of discrete (individual) molecules.The bonds between the molecules are weaker than the covalent bonds within molecules. e.g. CO2

O=C=OO=C=OO=C=OO=C=OWeak intermolecular forces (Van der Waals)Strong covalent intramolecular bondsNote: The intermolecular forces are weak BONDS (Van der Waals) between the molecules.

All discrete molecules have low melting points because only weak intermolecular bonds are broken (Van der Waals)- not covalent bonds.2. Covalent NetworksThese consist of a giant lattice of covalently bonded atoms. e.g. Carbon (diamond)

Covalent bondCarbon atomAll covalent networks have very high melting points because strong covalent bonds must be broken.

=Oxygen atoms=Silicon atomsStarterDraw the bonding diagrams for the followingH2OCF4NH3HF

Revision of IonsAll atoms become more stable if they have a full outer shell of electrons (like the noble gases).

During chemical reactions, atoms can lose electrons or gain electrons. When this happens the atoms become electrically charged particles called ions.

Atoms that lose electrons form positive ionsAtoms that gain electrons form negative ions.

Ion:Particle found when an atom loses or gains electron(s).Ionic CompoundsContain metal and non-metal ions.Contain oppositely charged ionE.g. Sodium chlorideNa+Cl-Magnesium sulphateMg2+SO42-Remember ions are charged because the dont have the same numbers of protons and electrons.Ca2+P3-Positive charge therefore more protons than electrons.Negative charge therefore less protons than electrons.20 protons (atomic number)18 electrons15 protons (atomic number)18 electronsForming IonsAtomIon

NaNa+2,8,12,8AlAl3+2,8,32,8Metal atoms ALWAYS lose outer electrons to obtain a full shell when changing to ions.AtomIon

FF-2,72,8SS2-2,8,62,8,8Non-metals (except hydrogen) ALWAYS gain outer electrons to obtain a full shell when changing to ions.Group Number12345678Number of outer electronsCharge on ionExample of ionStarterDraw the bonding diagrams for the followingH2OCF4NH3HF

Forming Sodium ChlorideThe 2 atoms became ions:

Na+ Cl- 2,8 2,8,8

Structure of Ionic CompoundsAll ionic compounds are solid at room temperature with the ions being held in a fixed pattern called an IONIC LATTICE.

The ions cannot move and are held in place by the strong forces of attraction between the opposite charges.Ionic Bond: Electrostatic force of attraction between oppositely charged ions in a compound. Aim: To investigate the conductivity of different substances.

Method:Conductivity ExperimentBeaker containing compoundWiresPower supplyBulbElectrodes6 VResults:Name of substanceIs substance solid or in solutionDoes it have a metal in its name?Is the compound ionic, covalent or metallic?ConductorInsulatorSucrose (C12H22O11)Sucrose solution (C12H22O11)Polystyrene ([C8H8]n)Polystyrene in solutionSodium chloride solutionSodium chloride solidCopper sulphate solidCopper sulphate solutionZincConclusion:Ionic solutions conduct electricity.Ionic solids and covalent compounds do not conduct electricity.Metallic BondingMetals can lose their outer shell electrons to gain a stable electron arrangement. This is what happens in metals.

Outer electrons are said to be delocalised which allows them to move freely.

This effectively creates positively charged metal ions, which are surrounded by these delocalised electrons.

Metal atoms form positively charged ions and so they attract the free moving electrons in the lattice. This attraction forms a metallic bond which is very strong. Metallic Bond: The electrostatic force of attraction between the positive ions in a metallic lattice and the delocalised electrons within the structure.Aim: To investigate the conductivity of some metals and non-metals.

Method:Conductivity ExperimentWiresPower supplyMaterial to be tested6 VAAmmeterResults:Name of substanceIs substance a solid or liquid?Is substance a metal or a non-metal?ConductorInsulatorCopper foilIronSulphurMagnesiumSiliconOxygenAluminiumTinLeadCarbon (in form of graphite)Iodine Conclusion:All metals are conductors of electricity.Non-metals are insulators of electricity, except carbon in the form of graphite.Electrical Conductivity SummaryConductivity in Ionic CompoundsIonic compounds will conduct electricity when in solution or when molten (has been melted into a liquid) as the ions are free to move. An ionic compound in solution or as a melt is called an electrolyte. Solid ionic compounds do not conduct electricity because in the solid state the ionic lattice is rigid and the ions are not free to move. Conductivity in Covalent CompoundsCovalent solutions do not conduct electricity as they do not contain any charged particles.

The exception to this is carbon in the form of graphite which can conduct electricity as it has delocalised electrons.

Conductivity in MetalsAll metals are conductors of electricity whether they are in solid or liquid form.This is because they have electrons moving freely through their structures Non-metals are insulators of electricity, except carbon in the form of graphite.

StarterWhat type of bonding is present in the following compounds:a) sodium chlorideb) carbon dioxidec) potassium bromided) irone) Silicon dioxidef) chlorine

2. Explain why sodium chloride will not conduct in solid form, but will conduct when dissolved in water.Melting Points

Aim: To investigate the relationship between bonding and melting point.Method:Compound being testedResults:CompoundFormulaBondingMelting Point (oC)ShellacSilicaPotassium iodidecopperKISiO2C60H90O15CuCovalent discreteCovalent networkIonicMetallic77-120oC1723oC681oC1085oCConclusion:In generalIonic compounds High melting pointsMetallic elements High melting pointsCovalent networks High melting pointsCovalent compounds (discrete) Low melting pointsExplanation of Melting PointsTo melt a substance, the bonding between units (molecules and ionic structures) has to be substantially weakened (or partly broken). To boil a substance, these bonds have to be broken.

Ionic Compounds Example: sodium chloride have very high melting and boiling points and are all solids at room temperature. this is because ionic bonds need to be weakened/broken to melt or boil them.

Metallic ElementsExample: Iron

high melting and boiling points.

this is because metallic bonds need to be weakened/broken to melt or boil them.

Covalent Network SubstancesExample: Silicon dioxide

have high melting and boiling points and are all solids at room temperature. This is because the structure is held together by strong covalent bonds.

Discrete Covalent SubstancesExample: Carbon dioxide

have low melting and boiling points.

the Van der Waals forces that exist between covalent molecules are weak and when a discrete covalent substance is heated it is these weak forces that must be weakened or broken.

as these forces are weak they do not require much energy to break them and so melting and boiling points of discrete covalent substances are low.

N.B. the covalent bonds between atoms in a molecule are not broken during melting or boiling.

Almost all substances (except mercury) that exist as gases or liquids at room temperature, are discrete covalent substances.

Polar covalent substances have higher melting and boiling points than pure covalent substances due to the increased attraction between molecules.Conclusion:Some covalent substances dissolve in water, but most dissolve in other solvents.

Most ionic substance dissolve in water and this involves the lattice being broken up completely. Like dissolves likeThis means that non-polar solutes will dissolve in non-polar solvents polar solutes will dissolve in polar solventsionic solutes will dissolve in ionic/polar solvents

Ionic substances dissolve in water, but water isnt ionic, its covalent.

Remember- water has a special type of covalent bonding known as POLAR COVALENT.

This is an unequal sharing of electrons within the bond, leaving one end slightly polar +ve and the other end slightly polar ve.

This is not an ion, but a polarity. Water is still covalent.

Dissolving in water?When an ionic solid (salt) is added to water, the water molecules arrange themselves round the lattice with the polar +ve end attracted to the ve ion and the polar ve end attracted to the +ve ion.

If enough energy is present, the ionic lattice breaks and the compound dissolves.

If there is not enough energy then the solid doesnt dissolve i.e. the solid is insoluble.

Some covalent compounds also dissolve in water.

These compounds must also have polar covalent bonding.

FORMULAE AND REACTION QUANTITIES State SymbolsState symbols are used in order to show what state a substance is in, suffixes are used;

Elements/substances that are solids are often given the suffix (s) e.g. Ca (s) or Calcium (s)

Elements/substances that are liquids are often given the suffix (l)e.g. Hg (l) or Mercury (l)

Elements/substances that are gases are often given the suffix (g)e.g. Ar (g) or Argon (g)

Elements/substances that are dissolved in water are often given the suffix (aq)e.g. Br2 (aq) or bromine (aq)

Chemical SymbolismChemical FormulaeChemical formula gives elements involved in a compound and the number of each atom of an element in the compound.e.g. H2O: 2 hydrogen atoms and 1 oxygen atom per molecule.Working Out Formulae Using ValenciesThe chemical formula for a compound can always be worked out by considering the bonding. There is a shorter method which uses the combining powers (valency).Group12345678Valency12343210Formulae RulesNnameSsymbolsVvalencySswapCcancel out common factorFformulaSimple Formulae1. Nitrogen hydridenamenitrogen hydrogensymbolsNHvalency31swap13cancel out common factor13formula NH32. Silicon oxidename silicon oxygensymbolsSiOvalency42swap24cancel out common factor12formula SiO23. Phosphorous iodidename phosphorous iodinesymbolsPIvalency31swap13cancel out common factor13formula PI3Answer Questions Textbook pg 57 Q1Formulae from PrefixesIf a formulae has prefixes in the name, you do not use formulae rules to work out the formula.Prefixes:Mono 1Di 2Tri 3Tetra 4Penta 5Hexa- 6ExamplesCompoundFormulaSulphur dioxideCarbon tetrachlorideDinitrogen tetraoxideNitrogen trihydridePhosphorus pentachlorideSO2CCl4N2O4NH3PCl5Answer Questions Textbook pg 58 Q3Transition Metal Valencies using Roman NumeralsThe block of metals in the centre of the Periodic Table are the Transition Metals.Transition metals can have more than one valency.Their valency is shown by using Roman Numerals, in the name of the compound.E.g. Iron (III) oxide contains iron with a valency of 3.NumberRoman Numeral1I2II3III4IV5V6VI1. Iron (III) chloridename iron chlorinesymbols FeClvalency 3 1swap 1 3cancel out common factor 1 3formula FeCl32. Zinc (II) oxidename zinc oxygensymbols ZnOvalency 2 2swap 2 2cancel out common factor 1 1formula ZnOAnswer Questions Textbook pg 61 Q5Compounds ending in ate or iteThese compounds contain 2 elements and oxygen.Magnesium sulphateLithium carbonateSodium hydroxide special case

SulphateCarbonateHydroxideNitrate}These substances are known as COMPLEX ions which have more than one element present.

Their formula and VALENCY can be found on databook.Charge = Valency1. Sodium sulphate (pg data book)name sodium sulphatesymbolsNaSO4valency12swap21cancel out common factor21formula Na2SO42. Magnesium nitrate (data book)name magnesium nitratesymbols MgNO3valency21swap12cancel out common factor12formula Mg(NO3)2N.B. Brackets are required here because there is more than one nitrate ion.3. Ammonium carbonate (data book)name ammonium carbonatesymbols NH4CO3valency 1 2swap 2 1cancel out common factor 2 1formula (NH4)2CO3N.B. Brackets are required here because there is more than one ammonium ion.Ionic FormulaeRevision of Ionic CompoundsIonic compounds contain oppositely charged ions.E.g. Sodium chloride Na+Cl-Magnesium sulphate Mg2-SO42-Ions are charged because they dont have the same numbers of protons + electrons.Ca2+P3-Positive charge therefore more protons than electronsNegative charge therefore less protons than electrons20 protons (atomic number) 18 electrons15 protons (atomic number) 18 electronsForming ions AtomIon NaNa+ 2,8,1 2,8

AlAl3+ 2,8,3 2,8Metals ALWAYS lose outer electrons to obtain a full shell when changing to ions. AtomIon FF- 2,7 2,8

SS2- 2,8,6 2,8,8Non-metals (except H2) ALWAYS gain outer electrons to obtain a full shell when forming ions.Group number1234567Charge on ion1+2+3+/3-2-1-Valency1234321Valency = ChargeIonic FormulaeThe ionic formulae of a compound is just the chemical formula with the charges on the ions shown.Chemical FormulaIonic FormulaNaClNa+Cl-MgOMg2+O2-CaFCa2+(F-)21. Magnesium oxidenamemagnesium oxygensymbols of ionsMg2+O2-valency22swap22cancel out common factor11formula Mg2+O2-N.B. no brackets required as only 1 of each ion.Working out Ionic Formulae2. Potassium flouridenamepotassium fluoridesymbols of ionsK+F-valency11swap11cancel out common factor11formula K+F-N.B. no brackets required as only 1 of each ion.3. Aluminium oxidenamealuminium oxygensymbols of ionsAl3+O2-valency32swap23cancel out common factor23formula (Al3+)2(O2-)3N.B. Brackets are required here as there are more than 1 of each ion.3. Copper (II) chloridename copper chloridesymbols of ionsCu2+Cl-valency 2 1swap 1 2cancel out common factor 1 2formula Cu2+(Cl-)2N.B. Brackets are required here as there are more than 1 chloride ion.1. Lithium carbonate (pg4 data book)name lithium carbonatesymbols of ions Li+CO32-valency12swap21cancel out common factor21formula (Li+)2CO32-N.B. Brackets are required here as there is more than 1 lithium ion.Group Ions Ionic Formulae2. Ammonium sulphate (pg4 data book)name ammonium sulphatesymbols of ions NH4+ SO42-valency12swap21cancel out common factor21formula (NH4+)2SO42-N.B. Brackets are required here as there is more than 1 ammonium ion.Answer Questions Textbook pg 63 Qs 8+9+10Word equationsReactants ProductsAlways shown on left hand side- These are the starting materials for the reaction.Always shown on right hand side- These are the new substances formed in the reaction.Changes intoWe use word equations to describe what is happening in a chemical reaction.Burning of carbon with oxygen:carbon + oxygen carbon dioxide

2. Magnesium reacting with chlorine gas:magnesium + chloride magnesium chloride

3. Iron reacting with oxygen to produce iron oxideIron + oxygen iron oxide1. Write word equations for the reaction betweena) magnesium + oxygenb) sodium and chlorine

Answer magnesium + oxygen magnesium oxide

Sodium + chlorine sodium chloride

Formula EquationsThis is when we write the chemical formula for the substances.e.g.1. potassium hydroxide reacts with nitric acid to form potassium nitrate and water.

This can be written asPotassium hyroxide + nitric acid potassium nitrate + waterKOH + HNO3 KNO3 + H2O

2. Calcium hydroxide reacts with hydrochloric acid to produce calcium chloride and water.

This can be written as:

Calcium hydroxide+ hydrochloric acid calcium chloride + water

Ca(OH)2 + HCl CaCl2 + H2OChemical Formula You Must Know!Name of diatomic elementFormulaHydrogenH2NitrogenN2OxygenO2FluorineF2ChlorineCl2BromineBr2IodineI2Name of CompoundFormulaWaterH2OCarbon dioxideCO2Hydrochloric acidHClSulphuric acidH2SO4Nitric acidHNO3Sodium hydroxideNaOHAmmoniaNH3Chemical Formula You Must Know!Identifying atomsCompoundElementNo of atomsElementNo of atomsSalt (NaCl)

Sodium

1Chlorine 1Carbon dioxide (CO2)CarbonOxygenWater (H2O)HydrogenOxygenMethane (CH4)CarbonHydrogenHydrogen sulphide (H2S)HydrogenSulphurCalcium carbonate (CaCO3)CalciumCarbonOxygen

Identifying atomsCompoundElementNo of atomsElementNo of atomsSalt (NaCl)

Sodium

1Chlorine 1Carbon dioxide (CO2)Carbon1Oxygen2Water (H2O)HydrogenOxygenMethane (CH4)CarbonHydrogenHydrogen sulphide (H2S)HydrogenSulphurCalcium carbonate (CaCO3)CalciumCarbonOxygen

Identifying atomsCompoundElementNo of atomsElementNo of atomsSalt (NaCl)

Sodium

1Chlorine 1Carbon dioxide (CO2)Carbon1Oxygen2Water (H2O)Hydrogen2Oxygen1Methane (CH4)CarbonHydrogenHydrogen sulphide (H2S)HydrogenSulphurCalcium carbonate (CaCO3)CalciumCarbonOxygen

Identifying atomsCompoundElementNo of atomsElementNo of atomsSalt (NaCl)

Sodium

1Chlorine 1Carbon dioxide (CO2)Carbon1Oxygen2Water (H2O)Hydrogen2Oxygen1Methane (CH4)Carbon1Hydrogen4Hydrogen sulphide (H2S)HydrogenSulphurCalcium carbonate (CaCO3)CalciumCarbonOxygen

Identifying atomsCompoundElementNo of atomsElementNo of atomsSalt (NaCl)

Sodium

1Chlorine 1Carbon dioxide (CO2)Carbon1Oxygen2Water (H2O)Hydrogen2Oxygen1Methane (CH4)Carbon1Hydrogen4Hydrogen sulphide (H2S)Hydrogen2Sulphur1Calcium carbonate (CaCO3)CalciumCarbonOxygen

Identifying atomsCompoundElementNo of atomsElementNo of atomsSalt (NaCl)

Sodium

1Chlorine 1Carbon dioxide (CO2)Carbon1Oxygen2Water (H2O)Hydrogen2Oxygen1Methane (CH4)Carbon1Hydrogen4Hydrogen sulphide (H2S)HydrogenSulphurCalcium carbonate (CaCO3)Calcium1Carbon1Oxygen3

Balancing Formula EquationsThree things are balanced in a chemical equation:1. Atoms2. Mass3. Charge

When hydrogen burns in oxygen, water is formed. The formula equation for this reaction is:

H2 + O2 H2O

This equation is not balanced. The same amount of chemicals must be present on both sides of the reaction because atoms cannot be created or destroyed.

H2 + O2 H2OThere are more oxygen atoms on the left hand side than on the right hand side.

Steps to balance an equationPutting a number in front of formulae will multiply the number of atoms after it.

e.g. H2 + O2 H2O

LHS RHS2 H atoms4 H atoms2 O atoms2 O atoms

2. We need to fix the LHS now. Do this by putting a 2 in front on H on the LHS.. H2 + O2 2H2OLHS RHS4 H atoms4 H atoms2 O atoms2 O atoms22

More Balancing Equations1.

2.

3.

4.

Ionic EquationsReaction between magnesium + sulphuric acid

Word equationMagnesium + sulphuric acid magnesium sulphate + water

Chemical equationMg(s) +H2SO4(aq) MgSO4(aq)+H2(g)

Ionic equationMg(s)+2H+Cl-(aq) Mg2+(cl-)2(aq)+H2(g)

The MoleOne mole of a substance is equal to the formula mass expressed in grams.

It is also called the gram formula mass (GFM).

In the previous example for ammonium phosphate, the formula mass was calculated to be 149. This means that one mole of ammonium phosphate has the mass of 149g.The units for the mole is mol.

When working out calculations involving formula masses and moles, you can use the triangle below to convert from mass to moles.

mnFMHere n= no. of molesm= massFM= Formula massmnFMRearrange the triangle as follows:

m = n x FM

n = mFM = m FM nExample 1What is the mass of 2 moles of hydrogen chloride?

STEP 1: write the chemical formula. Symbols : H ClValency : 1 1Cross over valencies : 1 1Simplest ratio : 1 1Formula : HCl

STEP 2: calculate the gram formula mass. 1 x H = 1 x 1= 11 x Cl= 1 x 35.5= 35.5

So, Gram Formula mass = 36.5gThe formula mass of the compound hydrogen chloride is 36.5. This means that one mole of hydrogen chloride has a mass of 36.5g.

STEP 3: Rearrange triangle to calculate the mass.

m = n x FM

1 mole NaCl36.5g

m = n x FM 2 x 36.5 = 73g

Example 2Q. How many moles of copper (ll) carbonate are there in 494g of the substance?

A.STEP 1: write the chemical formula.Symbols : Cu2+ CO32-Valency : 2 2Cross over valencies : 1 1Simplest ratio : 1 1Formula : CuCO3

STEP 2: Calculate the GFM CuCO31 x Cu= 1 x 63.5= 63.51 x C = 1 x 12= 123 x O= 3 x 16= 48

So, Gram Formula Mass = 123.5g

STEP 3: Rearrange triangle for n.Use formula n= m/FM

So, n = m = 494 = 4 moles FM 123.5Therefore, 494g contains 4 moles of copper (ll) carbonate.

mnFMExample 3 (shortened answer)Q. Calculate the number of moles in 12.05g of magnesium sulphate.

Chemical Formula MgSO4

MgSO41xMg = 1 x 24.5 = 24.51xS = 1 x 32 = 324xO = 4 x 16 = 64 GFM = 120.5n = m = 12.05 = 0.1 moles FM 120.5

Therefore, there are 0.1 moles in 12.05g in magnesium sulphate.

mnFMMole RatiosCH4 + O2 CO2 + H2O

We can use the mole ratios from balanced equations to calculate:

Mass of REACTANT required for a reaction.Mass of PRODUCT formed.221 mole2 moles1 mole2 molesMole Ratio CalculationsQ. What mass of oxygen is needed to react with 2.4g of carbon.

A. C + O2 CO2 C : O2 1 mole:1 mole12g:32g 1g :32/12 2.4g:32/12 x 2.4 = 6.4g

Q. What mass of carbon dioxde is produced when 0.5 moles of propane is burned.

A. C3H8 + 5O2 3CO2 + 4H2O C3H8 : CO2 1 mole:3 moles 1 mole:132g0.5 moles :0.5 x 132= 66gCO2 = 44g3CO2 = 132gQ. What mass of hydrogen is burned to produce 100g of water.

A. H2 + O2 H2O

1 mole H2:1 mole H2O1 mole H2O:1 mole H218g:2g1g:2/18g100g: 2/18 x 100= 11.11gH2 = 2gH2O = 18gACIDS AND BASES The pH ScaleThe pH scale is a continuous range of numbers from 1 to 14, which indicate the acidity or alkalinity of solutions.

Acids have a pH of less than 7 (pH7) Pure water and neutral solutions have a pH equal to 7 (pH=7)

The pH of a solution can be measured using universal indicator or pH paper. The pH of a solid cannot be measured it must first be dissolved in water or the pH paper dampened.Non-Metal OxidesWhen a non-metal elements burns in oxygen the non-metal oxide is formed.

Soluble non-metal oxides will dissolve in water to produce acidic solutions. e.g. CO2, NO2, SO2, SO3. Non-metal oxides which are insoluble, will not affect the pH.

Metal OxidesWhen metal elements burn in oxygen, the metal oxide is formed. e.g.

Soluble metal oxides will dissolve in water to form the metal hydroxide. e.g.

Metal oxides or hydroxides, which dissolve in water produce alkaline solutions.

Not all metal oxides are soluble. A general rule is that the oxides of the Group 1 and Group 2 metals produce alkaline solutions with water.

Ammonia gas (NH3), is soluble in water and will dissolve to produce an alkali.Insoluble metal oxides/hydroxides will not affect the pH of water.AcidsAcids are compounds which dissolve in water to form solutions which have a pH less than 7.The table below shows the most commonly used acids both in the lab and the home.Chemical NameFormulapHUsesHydrochloric acidHCl1-3Common lab acidNitric acidHNO31-3Common lab acidSulphuric acidH2SO41-3Common lab acidVinegarN/A 4-6Common household acidLemon juiceN/A 4-6Common household acidCar battery acidN/A 1-3Common household acidAcid solutions are made by adding a substance to water which will lower its pH. The substance added could be a solid, a liquid or a gas.

H+(aq) and Cl-(aq)

H+(aq) and SO42-(aq)

H+(aq) and HCOO-(aq)

The substance added is made up of molecules atoms of non-metal elements joined by covalent bonds.

When the substance is added to water the covalent bonds break to form ions which become attached to water molecules.

An acid solution is one which contains H+(aq) ionsAcid solutions are made by adding a substance to water which will lower its pH. The substance added could be a solid, a liquid or a gas.

Ions involvedH+(aq) and Cl-(aq)

H+(aq) and SO42-(aq)

H+(aq) and HCOO-(aq)

When the substance is added to water the covalent bonds break to form ions which become attached to water molecules.

An acid solution is one which contains H+(aq) ionsElectrolysis of AcidsAcids can be electrolysed and the products collected. REMEMBER: electrolysis is the breaking up of an ionic compound in solution or the molten state using electricity.

All acids contain the H+ ion. When electricity is passed through a solution of an acid the positively charged hydrogen ions are attracted to the negative electrode where they gain electrons to form hydrogen gas.AlkalisAlkalis are compounds which dissolve in water to form solutions which have a pH greater than 7.Chemical NameFormulapHUsesSodium hydroxideNaOH11-14Common lab alkaliPotassium hydroxideKOH11-14Common lab alkaliCalcium hydroxideCa(OH)211-14Common lab alkaliCleaning fluidsN/A 8-14Common household alkaliToothpasteN/A 8-11Common household alkaliIndigestion tabletsN/A 8-11Common household alkaliWaterWater is a covalent compound.Covalent compounds do not conduct electricity.But we know that water can act as a conductorIt is believed that in pure water, and all aqueous solutions, a reversible reaction takes place.In water and aqueous solutions there is an equilibrium between hydrogen ions (H+) and hydroxide ions (OH-) and water molecules.

However, there are more water molecules than there are ions and so water conducts only slightly.

Pure water contains an equal concentration of hydrogen and hydroxide ions.H2O(l) H+(aq) + OH-(aq)To summarise:In water and any neutral solution, the concentration of H+ ions and OH- ions is equal and this gives a pH = 7 (neutral). In an acid solution the concentration of hydrogen ions (H+(aq)) is greater than the concentration of hydroxide ions (OH-(aq)). In an alkaline solution the concentration of hydroxide ions (OH-(aq)) is greater than the concentration of hydrogen ions (H+(aq)).In water and aqueous solutions there is an equilibrium between hydrogen ions (H+) and hydroxide ions (OH-) and water molecules.

However, there are more water molecules than there are ions and so water conducts only slightly.

Pure water contains an equal concentration of hydrogen and hydroxide ions.H2O(l) H+(aq) + OH-(aq)To summarise:In water and any neutral solution, the concentration of H+ ions and OH- ions is equal and this gives a pH = 7 (neutral). In an acid solution the concentration of hydrogen ions (H+(aq)) is greater than the concentration of hydroxide ions (OH-(aq)). In an alkaline solution the concentration of hydroxide ions (OH-(aq)) is greater than the concentration of hydrogen ions (H+(aq)).Diluting acids and alkalis Adding water to an acid increases the pH of the solution towards 7, making it less acidic by decreasing the H+(aq) ions concentration. (The acidity decreases and the pH value increases).

Adding water to an alkali decreases the pH of the solution towards 7, making it less alkaline by decreasing the OH-(aq) ions concentration. (The alkalinity decreases and the pH value decreases). Strength and ConcentrationStrength and concentration are terms that are often used incorrectly. They do not have the same meaning.

Strength is used to describe the extent of dissociation into ions.

Concentration is used to describe the number of moles of solute in a certain volume of solution.ConcentrationThe concentration of a solution is the number of moles of solute present in one litre of solution i.e. moles per litre (mol l-1).

A 1 mol l-1 solution is made by dissolving 1 mole of the substance in 1 litre of solution.so nCVVolume of solution in litresConcentration of solution in mol l-1Number of moles of solute

Sometimes, before calculating the concentration, there is a need to convert grams into moles.mnGFMGram formula mass Number of moles of soluteMass in gramsExample calculation using Concentration TriangleQ. Calculate the concentration of a 500cm3 solution that contains 0.1 moles.

A. V= 500cm3 = 0.5ln= 0.1 molesc= ?From trianglec= n/v = 0.1 / 0.5= 0.2 mol l-1 solution

Therefore the concentration is 0.2 mol l-1.nCVExample calculation using both trianglesQ. Calculate the mass of sodium hydroxide required to prepare 2 litres of 0.015 mol l-1 solution.

A. Look at the information were given first:V= 2 litres = 2lc= 0.015 mol l-1n=?First we will calculate nn= c x v = 0.015 x 2 = 0.03 molesNow we know the number of mole, we can use the other triangle

n= 0.03 molesFM= NaOH = 23+16+1= 40m= ?m= n x FM = 0.03 x 40 = 1.2g

Therefore the mass of sodium hydroxide is 1.2gmnGFMReactions of AcidsNeutralisationWhen you add a base to an acid, the acid is slowly cancelled out or neutralised. The reaction of acids with alkalis is an example of a neutralisation. Neutralisation: reaction that moves the pH of an acid toward 7 Any substance which neutralises an acid by reacting with the hydrogen ions (H+) of the acid to form water.Bases: metal oxides, metal hydroxides and metal carbonates.Neutralisation will move the pH of an acid up towards 7 and the pH of an alkali down toward 7.BasesWe will look at 4 different neutralisation reactions;

Reactions of Acids with AlkalisWhen an acid is neutralised by an alkali, a salt and water are formed.Remember: an alkali is a soluble metal oxideThe general word equation to represent this reaction is;

acid + alkali salt + water

In the reaction of an acid with an alkali the hydrogen ions and hydroxide ions form water.Nitric + sodium sodium + water acidhydroxide nitrate

HNO3 + NaOH NaNO3 + H2OReactions of Acids with Metal OxidesWhen a metal is burned the metal oxide is formed. If that metal oxide dissolves in water it is called an alkali.Metal oxides which do not dissolve in water can still neutralise an acid.Acids react with metal oxides to form a salt and water.Acid + metal oxide salt + water

In the reaction of an acid with a metal oxide the hydrogen ions and the oxide ions form water.

Reaction of Acids and Metal CarbonatesWhen an acid reacts with a metal carbonate a salt, water and carbon dioxide are formed.

The H+ ions from the acid react with the CO32- from the metal carbonate to form CO2 and H2O.

Test for CO2: Limewater turns milky if carbon dioxide if present.Reactions of Acids and MetalsMost metals react with acids to form a salt and hydrogen gas.

The reaction that occurs is a neutralisation reaction.Copper, mercury, gold, silver and platinum do not react with acids.

In the reaction between a metal and an acid, the hydrogen ions of the acid from hydrogen molecules.

Test for H2: Hydrogen burns with a pop!Acid RainFossil fuels can burn to produce sulphur dioxide (SO2).

Nitrogen dioxide (NO2) is produced by the sparking of air in car engine.

Both SO2 and NO2 dissolve in water in the atmosphere to produce acid rain.

Acid rain damagesBuildings made from carbonate rock by eroding them.

Structures made of iron and steel by making them corrode.

Plant life by making the soil too acidic.

Animal life by making the water in ponds and lakes too acidic.

Volumetric TitrationsThe concentration of acids/alkalis can be calculated from the results of volumetric titrations.

White tileConical flask with alkali solution e.g. sodium hydroxide (NaOH) + universal indicatorAcid solution e.g. dilute hydrochloric acid (HCl)Burette

Pipette Pacid x Vacid x Cacid = Palkali x Valkali x CalkaliP= powerV= volume in litres C= concentrationPower of an acid is the number of H+ ions.For HCl, p=1For H2SO4, p=2For HNO3, p=1Power of an alkali is the number of OH- ions.For NaOH, p=1For Ca(OH)2, p=2For Al(OH)3, p=3Example 1In a titration 10cm3 of sodium hydroxide solution with a concentration of 0.2 mol l-1 was neutralised by 25 cm3 of dilute hydrochloric acid. Calculate the concentration of the acid solution in moles per litre.Pacid x Vacid x Cacid = Palkali x Valkali x Calkali1x 0.025 x Cacid = 1 x 0.01x 0.21x 0.025 x Cacid = 1 x 0.01x 0.20.025 x Cacid = 0.002Cacid = 0.002 / 0.025Cacid = 0.008 mol l-1Example 2What volume of 2M sodium hydroxide will be required to neutralise 40cm3 of 2M sulphuric acid?Pacid x Vacid x Cacid = Palkali x Valkali x Calkali2 x 0.04 x 2 = 1 x Valkali x 20.16 = Valkali x 2Valkali = 0.16 / 2Valkali = 0.08 litresValkali = 80 cm3Example 3What volume of 1M sulphuric acid will be needed to neutralise 2 litres of 0.1M potassium hydroxide?Pacid x Vacid x Cacid = Palkali x Valkali x Calkali2 x Vacid x 1 = 1 x 2 x 0.1Vacid x 2 = 0.2Valkali = 0.2 / 2Valkali = 0.1 lValkali = 100 cm3Everyday Examples of NeutralisationTaking antacid tablet to treat acid indigestion

Using lime (CaO) to reduce acidity in soil and lochs.

Preparation of Salts

SaltsSalts are ionic compounds which are produced in neutralisation reactions.They contain a positive ion, which comes from the acid (H+) and a negative ion, which comes from the neutraliser.Salt: a substance in which the hydrogen ion of an acid has been replaced by a metal ion (or the ammonium ion).Naming SaltsFirst part of the name comes from the metal in the alkali.Second part of the name comes from the acid.Hydrochloric acid always forms a chloride salt.Sulphuric acid always forms a sulphate salt.Nitric acid always forms a nitrate salt.AcidAlkaliSalt formedhydrochloric acidsodium hydroxidesulphuric acidcalcium hydroxidenitric acidammonium hydroxideSodium chlorideCalcium sulphateAmmonium nitrateSpectator IonsThe neutralisation of hydrochloric acid by sodium hydroxide can be shown as follows;

The Na+(aq) and Cl-(aq) ions are not changed. We call these ions spectator ions as they do not take part in the reaction.

If we remove the spectator ions from the equation, the ionic equation for the reaction is;

In the reaction of an acid with an alkali the hydrogen ions and hydroxide ions form water.More Spectator Ions

Omitting spectator ions...The spectator ions are SO42-(aq) and Mg2+Making Soluble SaltsUsing Soluble BasesSoluble salts can be prepared by reacting acids with alkalis or bases.When an acid is neutralised by a soluble base (alkali) a salt and water are produced.An indicator is used to show when the acid has been neutralised.E.g. Sodium chloride reacts with hydrochloric acid to produce sodium chloride (soluble salt) and water.

Using Metals and Insoluble Bases

It is easy to make soluble salts from acids using metals.e.g. magnesium chloride (soluble salt) can be made using hydrochloric acid and magnesium metal powder.Add metal powder to acid until no more reacts.Filter off unreacted metal powderEvaporate off the water to a small volume and then allow crystals to form naturally

The same filtration procedure can be used as above when producing a soluble salt using Acid + MetalAcid + Metal oxideAcid + Metal carbonate

Preparation of Insoluble Salts by Precipitation

Insoluble salts can be prepared by precipitation reactions. Precipitation Reaction: the reaction of two solutions to form an insoluble product called a precipitate.For example, silver iodide (insoluble salt) can be prepared by the following method; dissolve a soluble silver salt in waterdissolve a soluble iodide salt in watermix the two solutions together and a solid should formfilter the solution the solid will be retained in the filter paper and the solutionwash the solid with water and allow to dryThe reaction taking place in this experiment is:

The sodium nitrate formed is a soluble salt and so stays in solution.

omitting spectator ions

shows the ions which actually react