Question

Calculate the total pressure in a $10$ litre cylinder which contains $0.4g$ of helium, $1.6g$ of oxygen and $1.4g$ of nitrogen at ${27}^{\circ }C$. Also, calculate the partial pressure of helium gas in the cylinder. Assume ideal behaviour of gases:

[Given : $R=0.082litre-atm{K}^{-1}mo{l}^{-1}$.]

Answer 1

$n_{He}=\frac{0.4}{4}=0.1,n_{O_2}=\frac{1.6}{32}=0.05$

$n_{N_2}=1.4/28=0.05$

Partial pressure of helium,

$P_{He}\times V=n_{He}\times R\times T$

$P_{He}\times 10=0.1\times 0.0821\times 300$

$P_{He}=0.2463atm$

Total pressure,

$P\times V=(n_{He}+n_{O_2}+n_{N_2})RT$

$P\times 10=(0.1+0.05+0.05)\times 0.0821\times 300$

$P=0.4926atm$