Question

Density of dry air containing only N2 and O2 is 1.15g/L at 740 mm of Hg and 300k. What is ℅ composition of N2 by weight in the air.

Answer 1

Solution.

$$p \times V = \frac{m}{M} \times R \times T$$

$$\rho = \frac{m}{V}$$

$$p = \frac{\rho \times R \times T}{M}$$

$$M = \frac{\rho \times R \times T}{p}$$

$$M = \frac{g \times J \times K}{Liters \times mole \times K \times Pa}$$

$$Pa = \frac{J}{m^3}$$ $$m^3 = 1000 \times Liters$$

$$M = \frac{g \times J \times 1000 \times Liters}{Liters \times mole \times J}$$

M = 29.06 g/mole

$$w(N2) = \frac{28.01}{29.06}$$

w(N2) = 96.39 %

Answer:

w(N2) = 96.39 %