The electrolysis of aqueous solutions
4 marks · NormalDescribe the products formed at the electrodes during the electrolysis of concentrated sodium chloride solution, and test how you could confirm their presence.
State the product formed at the cathode and describe its relevant test.
State the product formed at the anode and describe its relevant test.
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) Hydrogen is formed at the cathode. The gas burns with a 'pop' when tested with a lighted splint.
(b) Chlorine is formed at the anode. Damp blue litmus paper turns white (bleached) when exposed to chlorine.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States hydrogen is formed at the cathode
B2 (a) · 1 mark · Describes the pop test with a lighted splint for hydrogen
B3 (b) · 1 mark · States chlorine is formed at the anode
B4 (b) · 1 mark · Describes using damp blue litmus paper or similar test to confirm chlorine
Worked solution
a. Hydrogen is formed at the cathode. To confirm its presence, hold a lighted splint near the gas; it will burn with a 'pop' sound.
b. Chlorine is formed at the anode. To confirm chlorine, expose damp blue litmus paper to the gas; it will turn white (bleached) due to chlorination.