Question

In the electrolytic dissociation of water, which of the following gases is collected at the anode?

[1 mark]

• A. Hydrogen
• B. Oxygen
• C. Carbon dioxide
• D. Ozone

Answer 1

The correct option is B Oxygen

Oxidation reaction takes place at the anode while reduction reaction takes place at the cathode. The following reaction takes place during the electrolytic dissociation of water:
$H_{2}O\left(l\right)\to H_2\left(g\right)+O_2\left(g\right)$
H goes from +1 oxidation state to 0 (addition of electron). Thus, it is a reduction reaction which takes place at the cathode.

O undergoes a change in the oxidation state from -2 to 0 (removal of electrons). Thus, it is an oxidation reaction which takes place at the anode.