Dry air contains $79 \% \mathrm{~N}_2$ and $21 \% \mathrm{O}_2$. At $T(\mathrm{~K})$, if Henry's law constants for $\mathrm{N}_2$ and $\mathrm{O}_2$ in water are $857 \times 10^4 \mathrm{~atm}$ and $4.56 \times 10^4 \mathrm{~atm}$, the ratio of mole fraction of $\mathrm{N}_2$ and $\mathrm{O}_2$ dissolved in water at 1 atm is

Distilled water boils at 373.15 K and freezes at 273.15 K . A solution of glucose in distilled water boils at 373.202 K . What is the freezing point (in K ) of the same solution? (For water, $K_b=0.52 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$, $K_f=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$ )

The vapour pressure of a pure liquid $A$ is 70 torr at 300 K . It forms an ideal solution with another liquid $B$. The mole fraction of $B$ is 0.2 and total vapour pressure of the solution is 84 torr at the same temperature. The vapour pressure of pure liquid $B$ (in torr) is