Question

At ${27}^{o}C$, a closed vessel contains equal weights of $He,C{H}_4$ and $S{O}_2$ exerts a pressure of 210 $mm$ and partial pressures of $He,C{H}_4$ and $S{O}_2$ are $P_1,P_2$ and $P_3$. Which one of the following is correct?

• A. $P_3>P_2>P_1$
• B. $P_1>P_2>P_3$
• C. $P_1>P_3>P_2$
• D. $P_2>P_3>P_1$

Answer 1

The correct option is B $P_1>P_2>P_3$

Partial pressure $\propto$ Mole fraction

Since weights of gases are equal, gas with lower molecular weight will have higher mole fraction and vice versa.

The higher the value of mole fraction, the more is the partial pressure.

The order of molecular weight: $M_{He}<M_{C{H}_4}<M_{S{O}_2}$

Therefore, the order of partial pressure: $P_1>P_2>P_3$

Hence, the correct answer is option $\text{B}$.