Question

The number of moles of oxygen obtained by the electrolytic decomposition of 108 g water is

• A. 2.5
• B. 3
• C. 5
• D. 7.5

Answer 1

Answer: (B)

$\underset{=36g}{\underset{2\times 18}{\underset{2\text{mole}}{2H_{2}O}}}\stackrel{\text{Electrolysis}}{\to }2H_2+\underset{1\text{mole}}{O_2}$
$\because$ $36g$ of ${\text{H}}_{\text{2}}\text{O}$ produce 1 mole of oxygen.
$\therefore$ 108 g of water will produce oxygen.
$=\frac{108}{36}=3mol$