The air is a mixture of a number of gases. The major components are oxygen and nitrogen with approximate proportion of 20% is to 79% by volume at 298 K. The water is in equilibrium with air at a pressure of 10 atm. At 298 K if the Henry’s law constants for oxygen and nitrogen at 298 K are 3.30 × 10 7 mm and 6.51 × 10 7 mm respectively, calculate the composition of these gases in water.

Question

Philoid · Accepted Answer

Given-

K_H for O₂ = 3.30 × 10⁷ mm Hg,

K_H for N₂ = 6.51 × 10⁷ mm Hg

Percentage of oxygen (O₂) = 20 %

Percentage of nitrogen (N₂) = 79%

Total pressure = 10 atm

Using Henry’s law,

→

where, p is the partial pressure of gas in the solution and K_H is Henry’s constant.

Now, to determine the mole fraction of oxygen in solution, , we use

To determine the mole fraction of nitrogen in solution, ,

Thus, the mole fraction of oxygen in solution, x_oxy = 4.61x10^-5

and the mole fraction of nitrogen in solution, x_nit is 9.22x10^-5