Question

A closed container contains $O_2$ gas at STP. An equimolar mixture of $N_2$ and $CO$ gas is introduced into the same container until its pressure becomes double of original value. Find the average molecular weight of the mixture.

• A. $20$
• B. $29$
• C. $31$
• D. $30$

Answer 1

The correct option is D $30$

As we know,
$P_o=X_{O_2}{P}_{O_2}+X_{N_2+CO}{P}_{N_2+CO}$
As pressure become double so, their mole fractions are equal in mixture.
Therefore, average molecular mass of mixture $=0.5\times 32+0.5\times 28=30$