The electrolysis of molten compounds
3 marks · NormalMolten sodium chloride (NaCl) is electrolysed using inert electrodes.
State the ions present in molten sodium chloride.
Write the balanced half-equation for the reaction at the cathode.
Identify the product formed at the anode and write the half-equation for its formation.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Na^+ ions and Cl^- ions
(b) Na^+ + e^- → Na
(c) Chlorine gas (Cl2) is formed; 2Cl^- → Cl2 + 2e^-
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States both Na^+ and Cl^- ions are present.
B1 (b) · 1 mark · Correct balanced half-equation for Na^+ at the cathode: Na^+ + e^- → Na
B1 (c) · 1 mark · Correct product (chlorine gas/Cl2) and correct half-equation: 2Cl^- → Cl2 + 2e^-
Worked solution
a) The ions present are Na^+ and Cl^-.
b) At the cathode, sodium ions gain electrons:
c) At the anode, chloride ions lose electrons to form chlorine gas:
So, chlorine is the product at the anode.