Question

When 20 mL of a sample of ozonised oxygen is passed through silent electric discharge, 15 mL of pure ozone gas is obtained. What was the volume of ozone in the original sample?

• A. 5 mL
• B. 10 mL
• C. 15 mL
• D. 18 mL

Answer 1

The correct option is A 5 mL

$3O_2⟶2O_3$

After conversion, total $O_3=15$

Let $x$ be $O_3$ in original sample, then $O_2$ in original sample= $(20-x)ml$

Hence, $(15-x)ml$ $O_3$ will be formed.

$O_2$ required= $\frac{3}{2}\times$($O_3$ formed)

$\Rightarrow 20-x=\frac{3}{2}(15-x)$

$\Rightarrow x=5ml$