Question

Let’s consider the solubility of a gas in a liquid, specifically carbon dioxide in water. We know that the solubility of a gas in a given solvent increases with pressure (think about an unopened soda). In many gas absorption processes (e.g., stripping, scrubbing) we will want to add or remove a solute from/to a gas phase. We want to calculate the solubility of CO2 in H2O, as a wt%, at a CO2 partial pressure of 200 kPa in the gas phase above water. Given: Henry’s Law constant

Answer 1

Since the critical temperature of CO2 is far above the normal room temperature hence we will have to make use of Henry's law

Henry's law is given by

Yi*P =Xi*Hi

Where Yi is the vapor mole fraction of the component

P is the total pressure of the system

Xi is the liquid mole fraction of the component

Hi is the Henry's constant of that component

Here the componenet is CO2

Henry's constnat for CO2 = 1.67*10⁸ Pa

Now we are provided with partial pressure of CO2 in gas phase

Partial pressure of CO2 in gas phase = Yi*P = 200 Kpa = 200000 Pa

now we will substitute all the known data in the Henry's law

200000 = 1.67*10⁸ *Xi

Xi =Xco2 = 0.00197

This will be mole fraction

XH2o = 1- 0.00197 = 0.998

Now we will connvert mole fration to weight fraction

xMCO2 =0.0008068

WEIGHT PERCENT OF CO2 = 0.0008068*100 = 0.08068 %