Question

The electrolytic decomposition of water gives ${\mathrm{H}}_2$ and ${\mathrm{O}}_2$ in the ratio of

• A. $1:2$ by volume
• B. $2:1$by volume
• C. $8:1$by mass
• D. $1:2$by mass

Answer 1

The correct option is B

$2:1$by volume

The correct option is option B

The explanation for the correct option:

1. An electrolytic decomposition reaction is a particular kind of reaction in which electrical energy is used as the activation energy to cause the reactant to break down.
2. The most common example of electrolytic decomposition is the electrolysis of water in which it splits into its constituent elements.
3. The reaction for electrolytic decomposition of water is $\underset{\mathrm{water}}{2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{hydrogen}}{2{\mathrm{H}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}$
4. According to Avogadro's hypothesis the equal volumes of any gas at the same temperature and pressure contain the same number of particles. i.e. Volume$\propto$moles
5. It is clear from the reaction that two volumes of hydrogen gas and one volume of oxygen gas are generated when water is electrolytically decomposed. i.e. ratio of hydrogen to oxygen is $2:1$by volume.

Final answer: The electrolytic decomposition of water gives ${\mathrm{H}}_2$ and ${\mathrm{O}}_2$ in the ratio of $2:1$by volume.