States of Matter - Result Question 1
####1. A mixture of $N_2$ and Ar gases in a cylinder contains $7 g$ of $N_2$ and $8 g$ of Ar. If the total pressure of the mixture of the gases in the cylinder is 27 bar, the partial pressure of $N_2$ is: [Use atomic masses (in g mol-1): $N=14, Ar=40$ ]
(a) 12 bar
(b) 15 bar
(c) 18 bar
(d) 9 bar
[2020]
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Solution:
- (b) $n _{N_2}=\frac{7}{28}=\frac{1}{4}=0.25$
$n _{\text{Ar }}=\frac{8}{40}=\frac{1}{5}=0.20$
Now, applying Dalton’s law of partial pressure,
$p _{N_2}=$ mole fraction of $N_2 \cdot P _{\text{Total }}$
$\frac{0.25}{0.45} \times 27=\frac{5}{9} \times 27=15$ bar
