Question

If a 2 litre flask of $N_2$ at ${20}^{o}C$ and 70 cm P is connected with a 3 litre of another flask of $O_2$ at the same temperature and 100 cm P. What will be the final pressure after the gases have throughly mixed at the same temperature as before? Also calculate the mole % of each gas in the resulting mixture. The volume stopcock may be neglected.

Answer 1

Let final pressure be p cm

number of mole of $N_2=\frac{PV}{RT}$

$n_1=\frac{70cm\times 2litre}{R\times {20}^{o}C}$

number of mole of $O_2=\frac{PV}{RT}$

$n_2=\frac{100cm\times 3litre}{R\times {20}^{\circ }C}$

final pressure = $\frac{(n_1+n_2)RT}{v}$

$=\frac{(\frac{70cm\times 2}{R\times {20}^{\circ }C}+\frac{100cm\times 3}{R\times {20}^{\circ }C})\times R\times {20}^{\circ }C}{3+2}$

$=170cm$

Mole %

$n_1=\frac{\frac{140}{20R}}{\frac{140}{20R}+\frac{300}{20R}}=35\%$

$n_2=65\%$