Question

Calculate the total pressure in a 10 litre cylinder which contains o.4g He,1.6g oxygen and 1.4g nitrogen at${27}^{0}C$. Also calculate the partial pressure of He gas in the cylinder. Assume ideal behavious for gases :

Answer 1

PV = nRT = 10 litre T = ${27}^0$ C = 300 K

nHe = $\frac{0.4}{4}=0.1$

$N_2$ = $\frac{1.4}{28}=0.05$

$O_2$ = $\frac{1.6}{32}=0.05$

So the total number of moles = 0.1 + 0.05 + 0.05 $\times 0.2$

P = 0.492 atm

Partial Pressure = Total Pressure$\times$ mole fraction

$P_{He}$= 0.492 $\left(\frac{0.1}{0.2}\right)$

= 0.246 atm is the partial pressure of He gas in then cylinder.

$P_{N_2}$ = 0.492 $\left(\frac{0.05}{0.2}\right)$

= 0.123 atm is the partial pressure of nitrogen gas in then cylinder.

$P_{O_2}$ = 0.492 $\left(\frac{0.05}{0.2}\right)$

= 0.123 atm is the partial pressure of oxygen gas in then cylinder.