Question

16 g of $O_2$ and 8 g of $He$ is present in a closed container. If total pressure of the mixture of gases in the cylinder is 15 atm then the partial pressure of $He$ in the cylinder will be:

• A. 3 atm
• B. 10 atm
• C. 6 atm
• D. 12 atm

Answer 1

The correct option is D 12 atm

Mole of $O_2=\frac{16}{32}=0.5$
Mole of $He=\frac{8}{4}=2$
Partial pressure of $He=$ Mole fraction of He $\left(X_{He}\right)\times$ total pressure $\left(P_T\right)$
Partial pressure of $He=\frac{2}{2.5}\times 15=12atm$