Chemical Changes and Structure Neutralisation

Learning Intentions We are learning about the uses of acids in food and drink and the impact on our health. We are learning about different examples of chemicals used to neutralise acids. We are learning to predict the chemicals produced during neutralisation reactions

Success Criteria I can give examples of food and drinks that are acidic and the effect that they have on our health. I can carry out experiments and write chemical reactions between acids and metals; metal oxides; carbonates and alkalis. I can state the meaning of the term base and give different examples of bases. I can predict the products or reactants involved in neutralisation reactions

Neutralising acids Method Add about 10cm3 of acid to a small beaker Add 5 drops of pH indicator Add alkali until a colour change is observed

Neutralising acids Method Add about 10cm3 of acid to a small beaker Add 5 drops of pH indicator Add alkali until a colour change is observed Repeat with magnesium oxide instead of the alkali

Neutralising acids Result As the alkali was added, the colour changed from red to orange to green A solid neutraliser such as magnesium oxide also neutralised the acid but it took longer

Neutralisers Moves the pH of an acid upwards towards 7 Moves the pH of an alkali downwards towards 7 Can be used to assist us in dealing with problems caused by too much acid ie indigestion, acid soil

Neutralising acids with alkalis acid + alkali salt + water Salts are ionic compounds which can be produced by neutralisation reactions.

Neutralising acids with alkalis Eg HCl + NaOH NaCl + H2O From acid From neutraliser

Bases and alkalis A base is a substance which neutralises an acid Examples of bases include metal oxides, metal hydroxides, metal carbonates and ammonia An alkali is formed from a base which dissolves in water

Naming salts The first part of the name of the salt comes from the base eg Sodium hydroxide Magnesium oxide

Naming salts The acid gives the second part of the name of a salt Hydrochloric acid HCl chloride Nitric acid HNO3 nitrate Sulphuric acid H2SO4 sulphate

Naming salts - examples Sodium hydroxide neutralises nitric acid

Naming salts - examples Sodium hydroxide neutralises nitric acid

Naming salts - examples Sodium hydroxide neutralises nitric acid sodium nitrate

Naming salts - examples Magnesium oxide neutralises sulphuric acid

Naming salts - examples Magnesium oxide neutralises sulphuric acid

Naming salts - examples Magnesium oxide neutralises sulphuric acid magnesium sulphate

Naming salts - examples Nitric acid is neutralised by sodium hydroxide

Naming salts - examples Nitric acid is neutralised by sodium hydroxide

Naming salts - examples Nitric acid is neutralised by sodium hydroxide sodium nitrate

Naming salts - examples sulphuric acid + sodium hydroxide Magnesium oxide + nitric acid Hydrochloric acid + sodium hydroxide Lithium hydroxide + nitric acid

Naming salts - examples sulphuric acid + sodium hydroxide sodium sulphate Magnesium oxide + nitric acid magnesium nitrate Hydrochloric acid + sodium hydroxide sodium chloride Lithium hydroxide + nitric acid lithium nitrate

Ions with more than one atom valency 1 valency 2 valency 3 nitrate NO3- sulphate SO42- phosphate PO43- carbonate CO3-

Naming salts – using symbols Sodium hydroxide neutralises nitric acid

Naming salts – using symbols Sodium hydroxide + nitric acid NaOH + HNO3

Naming salts – using symbols Sodium hydroxide + nitric acid sodium nitrate + water NaOH + HNO3 NaNO3 + H2O

Naming salts – using symbols Sodium hydroxide + hydrochloric acid NaOH + HCl

Naming salts – using symbols Sodium hydroxide + hydrochloric acid NaOH + HCl NaCl + H2O

More examples NaOH + H2SO4 HNO3 + NaOH MgO + HCl

More examples NaOH + H2SO4 NaSO4 + H2O HNO3 + NaOH NaNO3 + H2O MgO + HCl MgCl + H2O

Reactions of acids with carbonates Add 20ml 1M hydrochloric acid to asmall glass beaker

Reactions of acids with carbonates Add 20ml 1M hydrochloric acid to a small glass beaker Add calcium carbonate using a spatula until the reaction stops

Reaction of acids with carbonates Carbonates react with acids to produce a salt, water and carbon dioxide gas. carbonate + acid salt + water + carbon dioxide

Carbonates - examples Calcium + hydrochloric calcium + water + carbon Carbonate acid chloride dioxide

Carbonates - examples Calcium + hydrochloric calcium + water + carbon Carbonate acid chloride dioxide CaCO3 + HCl CaCl2 + H2O + CO2

Reactions of acids with metals Add 1M hydrochloric acid to a boiling tube until it is approx. ¼ full

Reactions of acids with metals Add 1M hydrochloric acid to a boiling tube until it is approx. ¼ full Add 2 pieces of magnesium to the boiling tube

Reactions of acids with metals Add 1M hydrochloric acid to a boiling tube until it is approx. ¼ full Add 2 pieces of magnesium to the boiling tube Hold a lit wooden taper over the end of the boiling tube

Reactions of acids with metals Magnesium, aluminium, zinc, iron and tin react with acids to produce a salt and hydrogen metal + acid salt + hydrogen magnesium + hydrochloric magnesium + hydrogen acid chloride

Reactions of acids with metal oxides metal oxide + acid salt + water magnesium + hydrochloric magnesium + water oxide acid chloride

Reactions of acids with metal oxides metal oxide + acid salt + water magnesium + hydrochloric magnesium + water oxide acid chloride MgO + HCl MgCl2 + H2O

Salts as ionic compounds The salts produced by neutralisation reactions are ionic compounds – they contain ions. sodium NaCl Na+Cl- chloride

Salts as ionic compounds Ions are charged particles. They either have a positive or negative charge

Aqueous Ionic Compounds Ions separate in water and move around in solution as separate ions. Sodium chloride (Na+Cl-) could be represented as – Cl- Na+ Na+ Na+ Cl- Cl- Na+ Cl- Cl- Cl- Na+ Cl- Na+ Na+ Na+ Cl- Cl- Na+ Na+ Na+ Cl-

Chemical Tests The test for carbon dioxide is that it turns limewater cloudy

Chemical Tests The test for carbon dioxide is that it turns limewater cloudy The test for hydrogen is that it burns with a pop

Chemical Tests The test for carbon dioxide is that it turns limewater cloudy The test for hydrogen is that it burns with a pop The test for oxygen is that it relights a glowing splint

Electrolysis DC Carbon electrodes copper chloride

Electrolysis Copper forms at the negative electrode

Electrolysis Copper forms at the negative electrode The copper ion must be positive

Electrolysis Chlorine forms at the positive electrode

Electrolysis Chlorine forms at the positive electrode The chloride ion must be negative

Aqueous Ionic Compounds This can be represented as – Na+(aq) + Cl-(aq)

Ionic Equations Hydrochloric acid + sodium hydroxide sodium chloride + water

Ionic Equations Hydrochloric acid + sodium hydroxide sodium chloride + water HCl + NaOH NaCl + H2O

Ionic Equations Hydrochloric acid + sodium hydroxide sodium chloride + water HCl + NaOH NaCl + H2O H+(aq) + Cl-(aq) + Na+(aq) + OH-(aq) Na+(aq) + Cl-(aq) + H2O(l)

Ionic Equations - examples H2SO4 + Mg(OH)2 Ca(OH)2 + HNO3

Ionic Equations - examples H2SO4 + Mg(OH)2 MgSO4 + H2O Ca(OH)2 + HNO3

Ionic Equations - examples H2SO4 + Mg(OH)2 MgSO4 + 2H2O Ca(OH)2 + HNO3

Ionic Equations - examples H2SO4 + Mg(OH)2 MgSO4 + 2H2O 2H+(aq) + SO4-(aq) + Mg2+(aq) + 2OH-(aq) Mg2+(aq) + SO42-(aq) +2H2O(l) Ca(OH)2 + HNO3

Ionic Equations - examples H2SO4 + Mg(OH)2 MgSO4 + H2O 2H+(aq) + SO4-(aq) + Mg2+(aq) + 2OH-(aq) Mg2+(aq) + SO42-(aq) +H2O(l) Ca(OH)2 + 2HNO3 Ca(NO3)2 + 2H2O

Ionic Equations - examples H2SO4 + Mg(OH)2 MgSO4 + H2O 2H+(aq) + SO4-(aq) + Mg2+(aq) + 2OH-(aq) Mg2+(aq) + SO42-(aq) +H2O(l) Ca(OH)2 + 2HNO3 Ca(NO3)2 + 2H2O Ca2+(aq) + 2OH-(aq) + 2H+(aq) + 2NO3-(aq) Ca2+(aq) + 2NO3-(aq) + 2H2O(l)

Spectator Ions Some ions may be present on both sides of the equation in the same form. These are spectator ions. Ca2+(aq) + 2OH-(aq) + 2H+(aq) + 2NO3-(aq) Ca2+(aq) + 2NO3-(aq) + 2H2O(l)

Spectator Ions Some ions may be present on both sides of the equation in the same form. These are spectator ions. Ca2+(aq) + 2OH-(aq) + 2H+(aq) + 2NO3-(aq) Ca2+(aq) + 2NO3-(aq) + 2H2O(l)

Spectator Ions Some ions may be present on both sides of the equation in the same form. These are spectator ions. Ca2+(aq) + 2OH-(aq) + 2H+(aq) + 2NO3-(aq) Ca2+(aq) + 2NO3-(aq) + 2H2O(l) 2OH-(aq) + 2H+(aq) 2H2O(l)

Methods of salt preparation The product from the neutralisation of an acid with alkalis, metal oxides, hydroxides and carbonates is a SALT A salt would normally have a positive metal ion and a negative ion from the acid ie sulphate

Methods of salt preparation In setting out to make a salt we must consider is the salt we want soluble or insoluble how can we tell if the reaction is complete )ie neutral) if the salt is soluble, how do we remove the water how can we remove and dry an insoluble salt

Methods of salt preparation Information on the solublities of salts can be obtained from page 5 of the data book. Sodium and lithium salts are normally soluble ammonium salts are always soluble nitrate salts are always soluble

Methods of salt preparation Insoluble salts can be prepared by mixing two soluble chemicals which react together to give one insoluble solid or precipitate while the other ions remain in solution. The solid is obtained by filtering, washing and drying in air.

Methods of salt preparation Soluble salts can be made by neutralising an acid with an alkali eg potassium nitrate can be made by neutralising potassium hydroxide with nitric acid

Titration Titration uses the following equipment -

Titration Titration uses the following equipment - Conical flask burette pipette

Calculations moles = volume (l) x concentration (mol/l) moles = litres x mol/l m = v x c m v c

Calculations - example 20cm3 of hydrochloric acid was neutralised by 10cm3 of 2mol/l sodium hydroxide solution. What is the concentration of the acid?

Calculations - example 20cm3 of hydrochloric acid was neutralised by 10cm3 of 2mol/l sodium hydroxide solution. What is the concentration of the acid? write a balanced equation

Calculations - example hydrochloric acid + sodium hydroxide sodium chloride + water HCl(aq) + NaOH(aq) NaCl(aq) + H2O 1 mole 1 mole 1 mole 1 mole 1 mole of NaOH neutralises 1 mole of HCl

Calculations example 20cm3 HCl neutralises 10cm3 of 2 mol/l NaOH No of moles of NaOH is

Calculations example 20cm3 HCl neutralises 10cm3 of 2 mol/l NaOH No of moles of NaOH is m = v x c

Calculations example 20cm3 HCl neutralises 10cm3 of 2 mol/l NaOH No of moles of NaOH is m = v x c m = 0.01 x 2

Calculations example 20cm3 HCl neutralises 10cm3 of 2 mol/l NaOH No of moles of NaOH is m = v x c m = 0.01 x 2 m = 0.02 The number of moles of HCl also = 0.02

Calculations example 20cm3 HCl neutralises 10cm3 of 2 mol/l NaOH No of moles of NaOH is m = v x c m = 0.01 x 2 m = 0.02 The number of moles of HCl also = 0.02

Calculations - example No of moles of HCl = 0.02 m = v x c 0.02 v x 2 v = 0.01 litres or 10cm3

Learning Outcomes

Learning Outcomes