Question

If $N_2$ gas is bubbled through water at 293 K, how many milimoles of $N_2$ gas would dissolve in 1 Litre water. Assuming that $N_2$ exerts a partial pressure of 0.987 bar. Henry's constant = 76.8 Kbar

Answer 1

According to Henry's law,

$p_{N_2}=K_H.X_{N_2}$

$\Rightarrow x_{N_2}=\frac{0.987}{76800}=1.29\times {10}^{-5}$

Moles of water in $1L=\frac{1000}{18}=55.56$

Let us take the moles of nitrogen as $n$

Total moles $=n+55.56$

$\therefore$ $x_{N_2}=\frac{n}{n+55.56}=1.29\times {10}^{-5}$

$\Rightarrow n(1-1.29\times {10}^{-5})-55.56\times 1.29\times {10}^{-5}=0$

$\Rightarrow n=0.7\times {10}^{-3}=0.7$ milimoles