Question

In electrolysis of water:

(a) Name the gas collected at cathode and anode.
(b) Why is volume of one gas collected at one electrode is double of anode?
(c) Why are few drops of dilute $H_{2}S{O}_4$ added to water?

Answer 1

a) At cathode, $H_2$ is evolved and at anode $O_2$ is evolved.

b) At cathode, $H^{+}$ ion takes two electron to convert itself into $H_2$ gas. $2$ moles of $H^{+}$ gives $1$ mole of $H_2$.

$2H^{+}\left(aq\right)+2e^{-}\to H_2\left(g\right)$

At anode, $O{H}^{-}$ ion releases two electrons to convert into water and $O_2$. $2$ mole $O{H}^{-}$ gives $0.5$ mole $O_2$, i.e why volume of one gas collected at one electron is double of another.

c) Acid is added to make the water conduct electricity as the distilled water is a non-conductor of electricity.