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5.4.2.2Neutralisation of acids and salt production

AQA GCSE Combined Science (8464), Higher tier · Chemistry › Chemical changes › Reactions of acids

Practise Neutralisation of acids and salt production. 12 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.

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Revision notes

How acids are neutralised by alkalis, bases and metal carbonates to make salts, and how to work out the name and formula of the salt. Questions ask you to predict products, complete word and symbol equations, and work out formulae from ion charges.

Grade by grade

What you need to be able to do, from the first marks up to the top grade.

  1. 3
    Name the salt type from each acidHydrochloric acid gives chlorides, nitric acid gives nitrates and sulfuric acid gives sulfates.
  2. 4
    Predict products of acid with base or alkaliacid + metal oxide or metal hydroxide → salt + water.
  3. 4
    Predict products of acid with a carbonateacid + metal carbonate → salt + water + carbon dioxide.
  4. 5
    Tell the difference between bases and alkalisA base neutralises an acid; an alkali is a base that dissolves in water, such as a soluble metal hydroxide.
  5. 6
    Work out salt formulae from ion chargesBalance the charges so they add to zero, e.g. Ca2+ and NO3− give Ca(NO3)2.
  6. 7
    Write balanced equations for neutralisation reactionsFor example, CaCO3 + 2HCl → CaCl2 + H2O + CO2.

Notes

What neutralises an acid

  • Alkalis are soluble bases, e.g. soluble metal hydroxides such as sodium hydroxide and potassium hydroxide.
  • Bases include insoluble metal hydroxides, e.g. copper(II) hydroxide, and metal oxides, e.g. copper(II) oxide.
  • acid + alkali → salt + water
  • acid + base (metal oxide or metal hydroxide) → salt + water
  • acid + metal carbonate → salt + water + carbon dioxide. You see fizzing. Carbon dioxide turns limewater milky (cloudy).

Naming the salt

  • The first part of the name comes from the positive ion (the metal) in the base, alkali or carbonate.
  • The second part comes from the acid: hydrochloric acid → chloride; nitric acid → nitrate; sulfuric acid → sulfate.
  • Examples: copper(II) oxide + sulfuric acid → copper(II) sulfate + water; potassium hydroxide + nitric acid → potassium nitrate + water.

Formulae and equations

  • Learn these ions: Cl−, NO3−, SO42−, OH−, CO32−, O2−, Na+, K+, Mg2+, Ca2+, Cu2+, Zn2+, Al3+.
  • Balance the charges so the total is zero: NaCl, MgCl2, Na2SO4, CuSO4.
  • Use brackets when you need more than one of an ion made of several atoms: Ca(NO3)2, Al2(SO4)3.
  • 2NaOH + H2SO4 → Na2SO4 + 2H2O
  • ZnO + 2HNO3 → Zn(NO3)2 + H2O
  • CaCO3 + 2HCl → CaCl2 + H2O + CO2

Cheatsheet

  • acid + alkali → salt + water
  • acid + metal oxide or metal hydroxide → salt + water
  • acid + metal carbonate → salt + water + carbon dioxide
  • HCl → chlorides; HNO3 → nitrates; H2SO4 → sulfates
  • Alkali = a base that dissolves in water (e.g. NaOH, KOH)
  • Ions: NO3−, SO42−, CO32−, OH−, Cl−
  • Carbon dioxide test: limewater turns milky

How to answer each type of question

Name the salt and predict the products

1 to 4 marks4
  1. Metal part of the name from the base, alkali or carbonate.
  2. Ending from the acid: chloride, nitrate or sulfate.
  3. Add water, and carbon dioxide too if a carbonate reacts.

Example. (a) Name the salt formed when potassium hydroxide reacts with nitric acid.
(b) Name the salt formed when zinc carbonate reacts with sulfuric acid.
(c) Name the other two products of the reaction in (b).

Show the model answer
(a) potassium nitrate (1)
(b) zinc sulfate (1)
(c) water (1) and carbon dioxide (1)

Write the formula of a salt from its ions

1 mark each6
  1. Write the two ions with their charges.
  2. Find how many of each ion make the total charge zero.
  3. Put brackets round an ion of several atoms if you need more than one of it.

Example. Write the formula of:
(a) calcium chloride (Ca2+, Cl−)
(b) aluminium sulfate (Al3+, SO42−)
(c) magnesium nitrate (Mg2+, NO3−)

Show the model answer
(a) CaCl2 (1)
(b) Al2(SO4)3 (1)
(c) Mg(NO3)2 (1)

Write a balanced symbol equation for a neutralisation

2 marks7
  1. Write the correct formula for every reactant and product.
  2. Balance the metal and the acid's negative ion first, then hydrogen and oxygen.
  3. Count every atom on both sides.

Example. Magnesium carbonate reacts with dilute nitric acid.
Write a balanced symbol equation for this reaction.

Show the model answer
Correct formulae: MgCO3 + HNO3 → Mg(NO3)2 + H2O + CO2 (1)
Balanced: MgCO3 + 2HNO3 → Mg(NO3)2 + H2O + CO2 (1)

Shortcuts and memory tricks

  • Carbonate in, carbon dioxide out: any carbonate reacting with an acid fizzes and gives CO2.
  • Water is a product whenever an acid is neutralised by an alkali, a base or a carbonate.
  • Formula check: add up the charges; they must come to zero.

Where marks are lost

  • Leaving out carbon dioxide or water when a carbonate reacts.
  • Missing brackets, e.g. writing CaNO32 instead of Ca(NO3)2.
  • Calling every base an alkali: only bases that dissolve in water are alkalis.
  • Giving hydrogen as a product of an acid and a base: hydrogen only forms when an acid reacts with a metal.

Exam technique

  • 'Predict the products' means all the products, including water and carbon dioxide.
  • If the question gives you a formula, copy it exactly into your equation.
  • Decide the ending of the salt name from the acid first, then add the metal.

Quick recall

Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.

Name the salt produced when sodium hydroxide reacts with nitric acid.
sodium nitrate
Write a balanced symbol equation for the reaction of zinc carbonate, ZnCO3, with sulfuric acid.
ZnCO3 + H2SO4 → ZnSO4 + H2O + CO2
Write a balanced symbol equation for the reaction of potassium hydroxide with sulfuric acid.
2KOH + H2SO4 → K2SO4 + 2H2O
Write a balanced symbol equation for the reaction. Use M for the metal.
M2O3 + 3H2SO4 → M2(SO4)3 + 3H2O
Name the salt formed when potassium hydroxide reacts with hydrochloric acid.
potassium chloride
Write the general word equation for the reaction between a metal carbonate and an acid.
metal carbonate + acid → salt + water + carbon dioxide

Sample questions

Written for this site in the style of AQA exam questions. They are not taken from real past papers.

Question 1Easy4 marks
Acids react with bases, alkalis and carbonates to produce salts.
(a) Name the salt produced when sodium hydroxide reacts with nitric acid.[1]
(b) Name the salt produced when copper oxide reacts with sulfuric acid.[1]
(c) What are the products when calcium carbonate reacts with hydrochloric acid?
Tick (✓) one box.[1]
  • calcium chloride and water only
  • calcium chloride, water and carbon dioxide
  • calcium chloride and hydrogen
  • calcium hydroxide and carbon dioxide
(d) Which acid produces salts called chlorides?[1]
Show the answer and mark scheme
(a) Answer: sodium nitrate
  • sodium nitrate
(b) Answer: copper sulfate
  • copper sulfate / copper(II) sulfate
(c) Answer: calcium chloride, water and carbon dioxide
(d) Answer: hydrochloric acid
  • hydrochloric acid
Question 2Medium5 marks
Metal oxides, metal hydroxides and metal carbonates all neutralise acids.
(a) What is the difference between a base and an alkali?[1]
(b) Write a balanced symbol equation for the reaction of zinc carbonate, ZnCO3, with sulfuric acid.[2]
(c) Describe what you would see when green copper carbonate powder is added to dilute hydrochloric acid until no more reacts.[2]
Show the answer and mark scheme
(a)
  • an alkali is a base that dissolves in water / an alkali is a soluble base (e.g. a soluble metal hydroxide)
(b) Answer: ZnCO3 + H2SO4 → ZnSO4 + H2O + CO2
  • products ZnSO4 and H2O and CO2
  • ZnCO3 + H2SO4 → ZnSO4 + H2O + CO2 (all formulae correct)
(c)
  • fizzing / bubbles (of gas)
  • the green solid disappears / dissolves (until some is left over at the end)
  • the solution turns blue / blue-green
Question 3Hard7 marks
The salt produced when an acid reacts depends on the acid used and on the positive ions in the base, alkali or carbonate.
(a) Write a balanced symbol equation, including state symbols, for the reaction of solid aluminium oxide, Al2O3, with hydrochloric acid.[3]
(b) Write a balanced symbol equation for the reaction of potassium hydroxide with sulfuric acid.[2]
(c) A student wants to make lithium nitrate.
Suggest two different pairs of reactants the student could use.[2]
Show the answer and mark scheme
(a) Answer: Al2O3(s) + 6HCl(aq) → 2AlCl3(aq) + 3H2O(l)
  • correct products AlCl3 and H2O
  • balanced: Al2O3 + 6HCl → 2AlCl3 + 3H2O
  • state symbols (s), (aq), (aq), (l)
(b) Answer: 2KOH + H2SO4 → K2SO4 + 2H2O
  • products K2SO4 and H2O
  • balanced: 2KOH + H2SO4 → K2SO4 + 2H2O
(c)
  • lithium hydroxide and nitric acid
  • lithium carbonate and nitric acid / lithium oxide and nitric acid

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