Redox and Electrochemistry O Level

Which reaction is an example of a redox reaction?

• 2SO₂ + O₂ --> 2SO₃

• Ag⁺ + Cl^- --> AgCl

• CuO + H₂SO₄ --> CuSO₄ + H₂O

• H⁺ + OH^- --> H₂O

The reaction in which the same element is both oxidised and reduced is called a disproportionation reaction. Which equation is an example of a disproportionation reaction?

• 3Cu +8HNO₃ --> 3Cu(NO₃)₂ + 2NO + 4H₂O

• Cl₂ + 2NaOH --> NaCl + NaOCl + H₂O

• Fe₂(SO₄)₃ + 2KI --> 2FeSO₄ + K₂SO₄ + I₂

• 2Pb(NO₃)₂ --> 2PbO + 4NO₂ + O₂

The formation of metallic oxides involves the transfer of electrons from metal atoms to oxygen atoms. In the formation of one mole of which metallic oxide do the metal atoms not transfer exactly 2 moles of electrons?

• aluminium oxide

• iron(II) oxide

• magnesium oxide

• sodium oxide

Aluminium is obtained by electrolysis of molten aluminium oxide. Which statement about this electrolysis is correct?

• Aluminium ions are oxidised to aluminium at the negative electrode.

• Aluminium ions are oxidised to aluminium at the positive electrode.

• Aluminium ions are reduced to aluminium at the negative electrode.

• Aluminium ions are reduced to aluminium at the positive electrode.

4 different solutions were electrolysed in separated experiments. In one of the experiments, element X₂ was formed at the positive electrode. For which combination of solution and electrodes can the reaction for the formation of X₂ be represented by the equation shown below? 2X^- --> X₂ + 2e^-

• aqueous copper(II) sulfate with copper electrodes

• aqueous copper(II) sulfate with inert electrodes

• concentrated aqueous sodium chloride with inert electrodes

• dilute aqueous sodium chloride with inert electrodes

Dilute aqueous sodium chloride and concentrated aqueous sodium chloride are electrolysed using inert electrodes in separate experiments. Which row shows the products of these experiments?

• A

• B

• C

• D

Write the ionic half equation for the reaction that happens at the anode.

(a)  

Describe a simple test that would confirm the identity of the element formed at the anode. Include the result of the test in your answer.

(a)  

Dilute aqueous potassium chloride can also be electrolysed. Describe two differences between the products of the electrolysis of dilute aqueous potassium chloride and the products of the electrolysis of molten potassium chloride.

(a)  

Explain why different combinations of metals produce different voltages.

(a)