Question

The solubility of nitrogen gas at 25 degrees C and 1 atm is 6.8 x 10^(-4) mol/L. If the partial pressure of nitrogen gas in air is 0.76 atm, what is the concentration (molarity) of dissolved nitrogen?
5.2 x 10^(-4) M
1.1 x 10^(-5) M
4.9 x 10^(-4) M
3.8 x 10^(-4) M
6.8 x 10^(-4) M

Answer 1

Answer:

5.2 x 10⁻⁴ M.

Explanation:

• The relationship between gas pressure and the  concentration of dissolved gas is given by  Henry’s law:

P = kC

where P is the partial pressure of the gaseous  solute above the solution.

k is a constant (Henry’s constant).

C is the concentration of the dissolved gas.

• At two different pressures, there is two different concentrations of dissolved gases and is expressed in a relation as:

P₁C₂ = P₂C₁,

P₁ = 1.0 atm, C₁ = 6.8 x 10⁻⁴ mol/L.

P₂ = 0.76 atm, C₂ = ??? mol/L.

∴ C₂ = (P₂C₁)/P₁ = (0.76 atm)(6.8 x 10⁻⁴ mol/L)/(1.0 atm) = 5.168 x 10⁻⁴ mol/L ≅ 5.2 x 10⁻⁴ M.