Question

A gas mixture contains nitrogen and helium in 7 : 4 ratio by weight. The pressure of the mixture is 760 mm. The partial pressure of nitrogen is :

• A. 0.2 atm
• B. 0.8 atm
• C. 0.5 atm
• D. 0.4 atm

Answer 1

The correct option is A 0.2 atm

Let the weights be $7x$ and $4x$.
$P_{N_2}=P_{total}\times x_{N_2}$

$P_{N_2}=760\times \frac{\frac{7x}{28}}{\frac{7x}{28}+\frac{4x}{4}}$

$P_{N_2}=760\times \frac{1}{5}=152mm=\frac{152}{760}atm=0.2atm$.