Henry's Law Question

Question

The solubility of carbon dioxide in water is very low in air (1.05 x 10^-5) because the partial pressure of carbon dioxide in air is only 0.00030 atm. What partial pressure of carbon dioxide is needed to dissolve 100.0 mg of carbon dioxide in 1.00 L of water?

Answer 1

Henry's Law:

C = kP

C = concentration

k = Henry's constant

P = partial pressure

For the current problem, we need to look up Henry's constant for CO2. Found a value of 3.4x10^-2 M/atm.

Then we calculate the desired concentration (100.0 mg / L) in units of M (moles / L)

C = concentration = 100.0 mg / L x 1 g / 1000 mg x 1 mol CO2 / 44 g = 2.27x10^-3 mol / L = 2.27x10^-3 M

Solve for P (partial pressure)

P = C/k

P = 2.27x10^-3 M / 3.4x10^-2 M/atm

P = 0.067 atm