Question

The electrolytic decomposition of water gives ${\mathrm{H}}_2\mathrm{and}{\mathrm{O}}_2$ 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 explanation for the correct option:

Option(B): $2:1$ by volume

• An electrolytic decomposition reaction is a type of reaction in which the activation energy for the decomposition of the reactant is provided in the form of electrical energy.
• The electrolytic decomposition of water produces ${\mathrm{H}}_2\mathrm{and}{\mathrm{O}}_2$ , for which the reaction can be given as:
  $\underset{\left(\mathrm{Water}\right)}{2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}\stackrel{\mathrm{electricity}}{\to }\underset{\left(\mathrm{Hydrogen}\mathrm{gas}\right)}{2{\mathrm{H}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Oxygen}\right)}{{\mathrm{O}}_2\left(\mathrm{g}\right)}$
• From the above reaction it can be clearly observed that in the electrolytic decomposition of water, two volumes of hydrogen gas along with one volume of oxygen gas get formed in the reaction.
• Thus, the ${\mathrm{H}}_2$ and ${\mathrm{O}}_2$ gases are produced in the ratio of $2:1$ by volume during the process of electrolytic decomposition of water.

The explanation for the correct option:

Option(A): $1:2$ by volume

• The electrolytic decomposition of water gives does not give ${\mathrm{H}}_2\mathrm{and}{\mathrm{O}}_2$ in the ratio of $1:2$ by volume.
• Hence, the given option does not correspond to the correct concept.

Option(C):$8:1$ by mass

• The ratio of ${\mathrm{H}}_2\mathrm{and}{\mathrm{O}}_2$formed in the electrolytic decomposition of water is not given as $8:1$ by mass.
• Hence, the given option is the incorrect one.

Option(D):$1:2$ by mass

• The electrolytic decomposition of water gives does not give ${\mathrm{H}}_2\mathrm{and}{\mathrm{O}}_2$ in the ratio of $1:2$ by mass.
• Hence, the given option does not coincide with the correct concept.

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

Hence, option (B) is the correct answer.