Question

If the ratio of masses of $S{O}_3$ and $O_2$ gases confined in a vessel is $1:1$, then the ratio of their partial pressures would be :

• A. $5:2$
• B. $2:5$
• C. $2:1$
• D. $1:2$

Answer 1

The correct option is B $2:5$

Let $m$ be the mass of $S{O}_3$ and $O_2$ enclosed in the vessel.
Number of moles of $S{O}_3=\frac{m}{80}$

Number of moles of $O_2=\frac{m}{32}$

Partial pressure of $S{O}_3,P_A=\frac{m}{80}\times \frac{R\times T}{V}$

Partial pressure of $O_2,P_B=\frac{m}{32}\times \frac{R\times T}{V}$

Now, $\frac{P_A}{P_B}=\frac{m}{80}\times \frac{32}{m}=\frac{2}{5}$

Hence, the ratio of partial pressure of $S{O}_3$ and $O_2$ is $2:5$.