Henry's law with CO2

Question

You have a sealed 2 liter flask that contains nothing but water and carbon dioxide. The flask is half-filled with liquid water, has a temperature of 25°C, and the overall pressure within the flask is 0.1 atm. How many moles of CO₂ are in the flask? At this temperature, you may take the K_H value for CO₂ as 0.033 M / atm.

Answer 1

C = K_HP

C = concentration of CO₂ in solution = ?

K_H = Henry's law constant = 0.033 M/atm

P = partial pressure of CO₂ (see below)

To find partial pressure of CO₂, we look up the vapor pressure of water at 25ºC and find it to be ~0.031 atm

Partial pressure CO₂ = 0.1 atm - 0.031 atm = 0.069 atm

C = 0.033 M/atm x 0.069 atm = 0.00228 M

Since there is 1 L of water (half of the 2 L flask), the mols of CO₂ would be ...

0.00228 mol/L x 1 L = 0.00228 mols