Question

The Henry's law constant for the solubility of N₂ gas in water at 298K is 1.0 x 10⁵ atm. The mole fraction of N₂ is 0.8. The number of moles of N₂ from air dissolved in 10 moles of water at 298K and 5 atm pressure is

• A. 4 x 10^-4
• B. 4 x 10^-5
• C. 5 x 10^-4
• D. 4 x 10^-6

Answer 1

The correct option is A

4 x 10^-4

$P_{N_2}=P_T\times molefraction=5\times 0.8=4$
From Henry's law
$P_{N_2}=K_H\times X_{N_2}$
$X_{N_2}=4\times {10}^{-5}$
$X_{N_2}=\frac{n_{N_2}}{n_{N_2}+n_{water}}$
$n_{N_2}<<n_{water}$
$X_{N_2}=\frac{n_{N_2}}{n_{water}}$
$n_{N_2}=4\times {10}^{-4}$