IGCSE Electrolysis

Which statement best describes what happens to the electrons during electrolysis?

• They are added to chloride ions

• They are added to hydrogen ions

• They move through the circuit from negative to positive

• They move through the solution from negative to positive

Concentrated aqueous sodium chloride can be electrolysed. Which statement is correct?

• Hydrogen gas is formed at the anode, and chlorine gas is formed at the cathode.

• Hydrogen gas is formed at the cathode, and chlorine gas is formed at the anode.

• Sodium metal is formed at the anode, and chlorine gas is formed at the cathode.

• Sodium metal is formed at the cathode, and chlorine gas is formed at the anode.

Which statement about electrolysis is correct?

• Electrons move through the electrolyte from the cathode to the anode.

• Electrons move towards the cathode in the external circuit.

• Negative ions move towards the anode in the external circuit.

• Positive ions move through the electrolyte towards the anode during electrolysis.

At which electrodes is hydrogen produced?

• Electrode 1 only

• Electrodes 1 and 3

• Electrode 2 only

• Electrodes 2 and 4

Dilute sulfuric acid is electrolysed using inert electrodes. What are the products of the electrolysis?

• A

• B

• C

• D

What is the colour of the litmus at each electrode after five minutes?

• anode blue, cathode red

• anode red, cathode blue

• anode red, cathode colourless

• anode colourless, cathode blue

Four substances are electrolysed. The substances are concentrated aqueous sodium chloride, concentrated hydrochloric acid, molten lead (II) bromide and molten sodium oxide. Which statement about these electrolysis reactions is correct?

• A colourless gas is formed at the anode when molten sodium oxide is electrolysed

• A green gas is formed at the cathode when concentrated hydrochloric acid is electrolysed

• A metal is formed at the anode when molten lead (II) bromide is electrolysed

• A metal is formed at the cathode when concentrated aqueous sodium chloride is electrolysed

In which two experiments is a colourless gas evolved at the anode?

• 1 & 2

• 1 & 4

• 2 & 3

• 3 & 4

Which statement is correct?

• Copper metal is deposited at the positive electrode

• In the external circuit electrons move from negative to positive

• In the solution electrons move from positive to negative

• Oxygen gas is produced at the positive electrode

Concentrated aqueous potassium bromide solution is electrolysed using inert electrodes. The ions present in the solution are K⁺, Br^-, H⁺ and OH^-.

• A

• B

• C

• D