Question

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

• A. 49
• B. 47
• C. 46
• D. $47.9$

Answer 1

Answer: (C)

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