Question

Carbon monoxide gas is dissolved in water at 25⁰c and 0.01 atm. Henry’s law constant is 5.8 × 10⁴ atm.

The mole fraction of CO is…………..?

Answer 1

The mole fraction of a gas in solution is related to the partial pressure of the gas above the solution by Henry’s law.

Henry's law states that the concentration of dissolved gas is directly proportional to the partial pressure of that gas above the solution.

P ∝ C (or) P = k_H.C

Where,

• ‘P’ denotes the partial pressure of the gas in the atmosphere above the liquid.
• ‘C’ denotes the concentration of the dissolved gas.
• ‘K_H’ is Henry’s law constant of the gas.

In a question, it is given,

P - 0.01atm

T- 25⁰c

${\mathrm{K}}_{\mathrm{H}}$ - 5.8 × 10⁴ atm

Henry's Law states that “the partial pressure applied by any gas on a liquid surface is directly proportional to its mole fraction present in a liquid solvent.”

${\mathrm{\rho }}_{\mathrm{CO}}={\mathrm{\chi }}_{\mathrm{CO}}\times {\mathrm{K}}_{\mathrm{H}}$

Therefore,
$$\begin{gathered} {\mathrm{\rho }}_{\mathrm{CO}}={\mathrm{\chi }}_{\mathrm{CO}}\times {\mathrm{K}}_{\mathrm{H}} \\ {\mathrm{X}}_{\mathrm{CO}}=\frac{{\mathrm{\rho }}_{\mathrm{CO}}}{{\mathrm{K}}_{\mathrm{H}}} \\ =\frac{0.01\mathrm{atm}}{5.8\times {10}^4\mathrm{atm}} \\ =1.72\times {10}^{-7} \end{gathered}$$