AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
(HT only) Students should be able to: explain in terms of gain or loss of…
Full specification wording
Reactions of acids with metals: (HT only) Students should be able to: explain in terms of gain or loss of electrons, that these are redox reactions identify which species are oxidised and which are reduced in given chemical equations. Knowledge of reactions limited to those of magnesium, zinc and iron with hydrochloric and sulfuric acids.
In the reaction between a metal and an acid, the metal atoms lose electrons and are oxidised, while hydrogen ions from the acid gain electrons and are reduced.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 2 of 2
Study notes
From the checked teaching notes for this specification point.
The idea
In the reaction between a metal and an acid, the metal atoms lose electrons and are oxidised, while hydrogen ions from the acid gain electrons and are reduced. Because both oxidation and reduction occur together, the reaction is a redox reaction. For example, with magnesium and hydrochloric acid: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g). The magnesium loses two electrons to form Mg²⁺, so magnesium is oxidised. The hydrogen ions gain electrons to form H₂, so hydrogen is reduced. The same reasoning applies to zinc and iron with hydrochloric or sulfuric acid. To identify the species, compare the metal atom with its ion and the hydrogen ion with hydrogen gas, tracking electron loss and gain.
What earns the marks
- State that oxidation is loss of electrons and reduction is gain of electrons.
- Identify the metal as the species oxidised because it loses electrons to form positive ions.
- Identify hydrogen ions as the species reduced because they gain electrons to form hydrogen gas.
- Explain that a reaction is redox when both oxidation and reduction occur.
- Apply the explanation to magnesium, zinc or iron with hydrochloric or sulfuric acid.
Common mistakes and how to put them right
Saying hydrogen is oxidised because it is a product.
Put it right: Hydrogen ions gain electrons and are reduced.
Confusing the metal ion with the metal atom.
Put it right: Compare the metal atom, which loses electrons, with the metal ion formed.
Describing the reaction as only oxidation or only reduction.
Put it right: Both occur together, so it is a redox reaction.
Exam tips
- Write the half equations for the metal and for hydrogen to make electron transfer explicit.
- Use the phrase 'loss of electrons is oxidation, gain of electrons is reduction' in your explanation.
- Restrict examples to magnesium, zinc and iron with hydrochloric or sulfuric acid as required by the specification.
Try the lesson
The start of the Reactions of acids with metals: (HT only) Students should be able to: explain in terms of gain or loss of electrons, that these are redox reactions identify which species are oxidised and which are reduced in given chemical equations. Knowledge of reactions limited to those of magnesium, zinc and iron with hydrochloric and sulfuric acids. lesson, made from checked teaching notes for this specification point.
Have a go first
In the reaction Mg + 2HCl → MgCl₂ + H₂, which species is oxidised and why?
Listen
In the reaction between a metal and an acid, the metal atoms lose electrons and are oxidised, while hydrogen ions from the acid gain electrons and are reduced. Because both oxidation and reduction occur together, the reaction is a redox reaction. For example, with magnesium and hydrochloric acid: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g). The magnesium loses two electrons to form Mg²⁺, so magnesium is oxidised. The hydrogen ions gain electrons to form H₂, so hydrogen is reduced. The same reasoning applies to zinc and iron with hydrochloric or sulfuric acid. To identify the species, compare the metal atom with its ion and the hydrogen ion with hydrogen gas, tracking electron loss and gain. A strong answer earns marks for these points. State that oxidation is loss of electrons and reduction is gain of electrons. Identify the metal as the species oxidised because it loses electrons to form positive ions. Identify hydrogen ions as the species reduced because they gain electrons to form hydrogen gas. Explain that a reaction is redox when both oxidation and reduction occur. A common slip: Saying hydrogen is oxidised because it is a product. Instead, hydrogen ions gain electrons and are reduced. Exam tip: Write the half equations for the metal and for hydrogen to make electron transfer explicit.
See it
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Reactions of acids with metals: (HT only) Students should be able to: explain in terms of gain or loss of electrons, that these are redox reactions identify which species are oxidised and which are reduced in given chemical equations. Knowledge of reactions limited to those of magnesium, zinc and iron with hydrochloric and sulfuric acids.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge