AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Students should be able to: predict products from given reactants use the…
Full specification wording
Neutralisation of acids and salt production: Students should be able to: predict products from given reactants use the formulae of common ions to deduce the formulae of salts. AQA GCSE Chemistry 8462. GCSE exams Jun
This practical skill requires you to look at the reactants in a neutralisation or acid-carbonate reaction and work out what products form.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 3 of 3
Study notes
From the checked teaching notes for this specification point.
The idea
This practical skill requires you to look at the reactants in a neutralisation or acid-carbonate reaction and work out what products form. First identify the acid and the other reactant. The acid provides the anion for the salt: chloride from hydrochloric acid, nitrate from nitric acid, or sulfate from sulfuric acid. The other reactant provides the positive ion, such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Cu²⁺, Al³⁺ or NH₄⁺. Then combine these ions in the ratio that balances charge to write the salt formula. For example, aluminium oxide with hydrochloric acid gives aluminium chloride, AlCl₃, because three Cl⁻ balance one Al³⁺. Water is also produced, and carbon dioxide is produced if the reactant is a carbonate. Always check that the formula is electrically neutral.
What earns the marks
- Identify the acid and the other reactant from their names or formulae.
- State the anion supplied by the acid: Cl⁻, NO₃⁻ or SO₄²⁻.
- State the positive ion supplied by the base, alkali or carbonate, including its charge.
- Combine the ions in the simplest whole-number ratio that gives zero overall charge, and write the salt formula with correct subscripts.
- Name the salt using the positive ion name followed by the modified acid anion name.
- State the other products: water always, and carbon dioxide when a carbonate reacts with an acid.
Common mistakes and how to put them right
Writing the salt formula without balancing charges, such as AlCl for aluminium chloride.
Put it right: AlCl₃ because three chloride ions balance one aluminium ion.
Mixing up the endings for salts from different acids, such as calling a nitrate a nitride.
Put it right: Use -ate endings for these common oxyacids and -ide for hydrochloric acid.
Forgetting to include water as a product of neutralisation.
Put it right: Remember that hydrogen ions and hydroxide ions form water, and carbonate reactions also release carbon dioxide.
Using the formula of the acid as the formula of the salt, such as writing H₂SO₄ for a sulfate salt.
Put it right: Replace the hydrogen ions with the positive ion from the base.
Exam tips
- Underline the acid and the other reactant in the question before you start predicting products.
- Write the ions with their charges above the reactants to help you balance the salt formula.
- Check that the sum of positive charges equals the sum of negative charges in your final salt formula.
- If the question asks for products, include the salt, water, and carbon dioxide if a carbonate is present.
Try the lesson
The start of the Neutralisation of acids and salt production: Students should be able to: predict products from given reactants use the formulae of common ions to deduce the formulae of salts. AQA GCSE Chemistry 8462. GCSE exams Jun lesson, made from checked teaching notes for this specification point.
Have a go first
What is the chemical formula of the salt produced when solid magnesium oxide reacts with dilute hydrochloric acid?
Listen
This practical skill requires you to look at the reactants in a neutralisation or acid-carbonate reaction and work out what products form. First identify the acid and the other reactant. The acid provides the anion for the salt: chloride from hydrochloric acid, nitrate from nitric acid, or sulfate from sulfuric acid. The other reactant provides the positive ion, such as Na⁺, K⁺, Mg²⁺, Ca²⁺, Cu²⁺, Al³⁺ or NH₄⁺. Then combine these ions in the ratio that balances charge to write the salt formula. For example, aluminium oxide with hydrochloric acid gives aluminium chloride, AlCl₃, because three Cl⁻ balance one Al³⁺. Water is also produced, and carbon dioxide is produced if the reactant is a carbonate. Always check that the formula is electrically neutral. A strong answer earns marks for these points. Identify the acid and the other reactant from their names or formulae. State the anion supplied by the acid: Cl⁻, NO₃⁻ or SO₄²⁻. State the positive ion supplied by the base, alkali or carbonate, including its charge. Combine the ions in the simplest whole-number ratio that gives zero overall charge, and write the salt formula with correct subscripts. A common slip: Writing the salt formula without balancing charges, such as AlCl for aluminium chloride. Instead, AlCl₃ because three chloride ions balance one aluminium ion. Exam tip: Underline the acid and the other reactant in the question before you start predicting products.
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