5. Applications of Electrolysis -3

The diagram shows the electrolysis of lead(II) bromide using inert electrodes. Why does the bulb only light up when the lead(II) bromide is melted?

• Bromine atoms in lead(II) bromide are converted to ions when it is melted

• Electrons flow through the lead(II) bromide when it is melted

• The ions in lead(II) bromide are mobile charge carriers in the molten state.

• There are no ions in solid lead(II) bromide

What ions are present in molten aluminium oxide?

• Al³⁺, O^2-, H⁺, OH^-

• Al³⁺, O^2-

• Al³⁺, OH^-

Explain why the electrolyte has to be a liquid.

• So the ions can move
• So the electrons can move
• So that it doesn't get too hot
• So the fish are ok

The picture shows electrolysis of copper(II) sulphate solution using graphite electrodes. Besides formation of brown solid on the cathode, what other observations can be made?

• The mass of graphite anode decreases.

• The blue colour solution becomes paler.

• Bubbles of gas form at the anode.

• The blue colour solution becomes darker.

What is the half-equation for the discharge of hydroxide ions?

• 2O^2- --> O₂ + 4e^-

• OH^- --> OH + e

• 4OH^- --> 2H₂O + O₂ + 4e^-

• 2H₂O + O₂ + 4e^- --> 4OH^-

Choose the half-equation that shows the discharge of aluminium ion.

• Al³⁺ - 3e^- --> Al

• Al²⁺ + 3e^- --> Al

• Al³⁺ + 3e^- --> Al

• Al³⁺ --> Al + 3e^-

The diagram shows the electroplating of a steel object.

A student made the following statements.

1 The object turns a reddish-brown colour.

2 The copper sulfate solution changes to a paler blue colour.

3 The copper electrode becomes smaller.

Which statements are correct?

• 1, 2 and 3

• 1 and 2 only

• 1 and 3 only

• 2 and 3 only

Oxidation is loss of electron. Where does oxidation take place during electrolysis.

• At anode

• In the solution

• At the circuit

• At cathode

Which of the following statements are true about an electrolyte?

• it has ions that conduct electricity in the solid state

• it can conduct electricity in the molten state or in aqueous solution

• it is a compound with ionic bonds only

• it can be decomposed by electric current

When molten lead(II) iodide solution is electrolysed using carbon electrodes, which of the following represents the half-equation that occurs at the cathode?