According to Henry's Law, at a given temperature the concentration (C) of a gas dissolved in a liquid is proportional to the partial pressure (p) of the gas above the liquid. i.e
C = k*P-----------(1)
where k = Henry's constant
It is given that:
Concentration C of CO2 = 0.12 mol/L
k for CO2 at 25 C = 3.4 * 10^-2 mole/L.atm
Based on eq(1)
p(CO2) = C/k = 0.12 molL-1/3.4 *10^-2 molL-1atm-1
p(CO2) = 3.5 atm
