Question

The weight of $1$ L of ozonised oxygen at STP was found to be $1.5$ g. When $100$ mL of this mixture at STP was treated with turpentine oil, the volume reduced to $90$ mL. The molecular weight of ozone is :

• A. 49
• B. 47
• C. 46
• D. 47.9

Answer 1

Answer: (D)

47.9

Volume of $O_3$ in $100$ mL of ozonised $O_2$ $=100-90=10mL$ (dissolved in turpentine)
Volume of $O_3$ in 1 L of ozonised $O_2$$=\frac{10\times 100}{100}=100mL$
Volume of $O_2$ in 1 L $=1000-100=900mL$
Weight of 900 mL of $O_2$ at STP $=\frac{900\times 32}{22400}=1.286g$
Weight of 100 mL of $O_3$ at STP $=1.5-1.286$ $=0.214g$
Now, 100 mL of $O_3$ at STP weighs $0.214g$.
22400 mL of $O_3$ at STP weighs $\frac{0.214\times 22400}{100}$ $=47.94g$.
Molecular weight of $O_3=47.94$ g