Question

Equal amounts of two gases of molecular weight $4$ and $40$ are mixed. The pressure of the mixture is $1.1atm$. The partial pressure of the light gas in this mixture is:

• A. $0.55atm$
• B. $0.11atm$
• C. $1atm$
• D. $0.12atm$

Answer 1

The correct option is C $1atm$

No. of moles of lighter gas $=\frac{m}{4}$

No.moles of heavier gas $=\frac{m}{40}$

Total no. of moles $=\frac{m}{4}+\frac{m}{40}=\frac{11m}{40}$

Mole fraction of lighter gas $=\frac{\frac{m}{4}}{\frac{11m}{40}}=\frac{10}{11}$