IGCSE redox

The equations for two reactions of iodide ions are shown.

Which statement is correct?

• Both reactions are redox reactions.

• Neither reaction is a redox reaction.

• Only reaction 1 is a redox reaction.

• Only reaction 2 is a redox reaction.

When aqueous iron(III) chloride is added to aqueous potassium iodide a chemical reaction

occurs and iodine is formed.

Which statement is correct?

• Iodide ions are oxidised, they gain electrons in this reaction.

• Iodide ions are oxidised, they lose electrons in this reaction.

• Iron(III) chloride is oxidised in this reaction.

• Neither iodide ions nor iron(III) chloride is oxidised in this reaction.

The equation for the reaction between zinc and aqueous copper(II) sulfate is shown.

Zn + CuSO₄ → ZnSO₄ + Cu

Which statement is correct?

• The oxidation state of the oxidising agent has changed from 0 to +2.

• The oxidation state of the reducing agent has changed from 0 to +2.

• The oxidation state of the reducing agent has changed from +2 to 0.

• This is not a redox reaction. The solution changes from colourless to blue.

Chlorine displaces bromine from aqueous potassium bromide.

The ionic equation for the reaction is shown.

Cl₂ + 2Br^– → 2Cl^– + Br₂

Which statement about this reaction is correct?

• Bromide ions act as an oxidising agent.

• Bromide ions are oxidised when electrons are lost.

• Chlorine acts as a reducing agent.

• Chlorine is reduced when electrons are lost.

In the blast furnace, iron is formed when iron(III) oxide reacts with carbon monoxide in a redox

reaction.

Fe₂O₃ + 3CO → 2Fe + 3CO₂

Which substance is the oxidising agent and which substance is the reducing agent?

• A

• B

• C

• D

The equation for the reaction between iron(II) sulfate and bromine is shown.

6FeSO₄ + 3Br₂ → 2Fe₂(SO₄)₃ + 2FeBr₃

Which row identifies the oxidising agent and the reducing agent?

• A

• B

• C

• D

The reaction between magnesium and carbon dioxide is shown in the equation.

2Mg + CO₂ → 2MgO + C

Which statement describes what happens in this reaction?

• Carbon is oxidised.

• Magnesium is reduced.

• Neither oxidation nor reduction happens.

• The carbon in carbon dioxide is reduced

Which changes represent reduction?

• 1 and 2

• 1 and 3

• 1 only

• 2 only

Which changes represent oxidation?

• 1 and 2

• 1 and 3

• 1 only

• 2 only

The thermite reaction can be used to produce iron from iron(III) oxide.

The equation for the reaction is shown.

2Al + Fe₂O₃ → 2Fe + Al₂O₃

Which statements about this reaction are correct?

• 1 and 3

• 1 and 4

• 2 and 3

• 3 and 4