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What does neutralisation produce, and what are the products when acids react with metals, bases and carbonates?

Describe neutralisation in terms of hydrogen and hydroxide ions and write equations for reactions of acids with metals, bases and carbonates.

A focused answer to WJEC GCSE Chemistry topic 2.2, covering neutralisation as the reaction of hydrogen ions with hydroxide ions, and the products and equations when acids react with metals, with bases, and with carbonates.

Generated by Claude Opus 4.89 min answer

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  1. What this topic is asking
  2. Neutralisation in terms of ions
  3. Acid plus metal
  4. Acid plus base
  5. Acid plus carbonate
  6. Naming the salt
  7. Everyday neutralisation

What this topic is asking

WJEC topic 2.2 wants you to explain neutralisation in terms of hydrogen and hydroxide ions and to know the products and equations for the three main reactions of acids: with metals, with bases (including alkalis and metal oxides), and with carbonates.

Neutralisation in terms of ions

The result is a neutral solution (pH 7 if equal amounts react) containing a salt dissolved in water. The metal part of the base and the non-metal part of the acid combine to form the salt.

Acid plus metal

A reactive metal reacts with an acid to give a salt and hydrogen gas:

acid+metal→salt+hydrogen\text{acid} + \text{metal} \rightarrow \text{salt} + \text{hydrogen}

For example: Zn+H2SO4→ZnSO4+H2\text{Zn} + \text{H}_2\text{SO}_4 \rightarrow \text{ZnSO}_4 + \text{H}_2. You see bubbling as hydrogen is given off, and the hydrogen can be tested with a lighted splint (a squeaky pop).

Acid plus base

A base (a metal oxide or hydroxide) reacts with an acid to give a salt and water only:

acid+base→salt+water\text{acid} + \text{base} \rightarrow \text{salt} + \text{water}

For example: HCl+NaOH→NaCl+H2O\text{HCl} + \text{NaOH} \rightarrow \text{NaCl} + \text{H}_2\text{O}, and H2SO4+CuO→CuSO4+H2O\text{H}_2\text{SO}_4 + \text{CuO} \rightarrow \text{CuSO}_4 + \text{H}_2\text{O}. This is a neutralisation reaction.

Acid plus carbonate

A carbonate reacts with an acid to give a salt, water and carbon dioxide:

acid+carbonate→salt+water+carbon dioxide\text{acid} + \text{carbonate} \rightarrow \text{salt} + \text{water} + \text{carbon dioxide}

For example: 2HCl+CaCO3→CaCl2+H2O+CO22\text{HCl} + \text{CaCO}_3 \rightarrow \text{CaCl}_2 + \text{H}_2\text{O} + \text{CO}_2. You see fizzing as carbon dioxide is released, which turns limewater cloudy.

Naming the salt

Everyday neutralisation

Neutralisation is not just a lab reaction; it has many everyday uses. Indigestion remedies (antacids) contain a base such as magnesium hydroxide or calcium carbonate that neutralises excess hydrochloric acid in the stomach, relieving discomfort. Farmers add lime (calcium oxide or calcium hydroxide) to neutralise acidic soils so that crops grow better. Treatment works use bases to neutralise acidic industrial waste before it is released. In each case a base is chosen to react with an acid to bring the pH closer to 7. Recognising these examples helps you answer the "suggest a use" style questions that WJEC sometimes asks alongside the chemistry.

Exam-style practice questions

Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

WJEC sample3 marksWrite the word equation for the reaction of hydrochloric acid with calcium carbonate, and describe a test for the gas produced.
Show worked answer →

A Unit 2.2 structured question. Reward: the word equation is hydrochloric acid + calcium carbonate gives calcium chloride + water + carbon dioxide. The gas produced is carbon dioxide, tested by bubbling it through limewater, which turns cloudy (milky). Markers credit the three products (salt, water and carbon dioxide) and the limewater test turning cloudy. A common error is to forget water as a product or to give the wrong salt.

WJEC sample3 marksExplain, in terms of ions, what happens during the neutralisation of an acid by an alkali.
Show worked answer →

A Unit 2.2 explanation question. Reward: in neutralisation the hydrogen ions (H+\text{H}^+) from the acid react with the hydroxide ions (OH−\text{OH}^-) from the alkali to form water: H++OH−→H2O\text{H}^+ + \text{OH}^- \rightarrow \text{H}_2\text{O}. The products are a neutral solution of a salt and water. Markers credit naming the two ions and the ionic equation forming water. A common slip is to write a full molecular equation without the key H++OH−\text{H}^+ + \text{OH}^- idea the question asks for.

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