Question

If the boiling point of an aqueous solution is ${100.1}^{o}C$. What is its freezing point? Given latent heat of fusion and vaporisation of water are $80cal$ $g^{-1}$ and $540cal$ $g^{-1}$ respectively

Answer 1

Given ,

latent heat of fusion = 80 cal /g

latent heat of vaporisation = 540 cal /g

$k_b=\frac{R{T}^2}{1000l_v}$

putting values we get ,

$k_b=0.513$

$\Delta T_b=0.1$ and $k_b=0.513$

$\Delta T_b=k_b\times m$

0.1 = 0.513 m $\Rightarrow m=\frac{0.1}{0.513}$

$\Delta T_f=k_{f}m$

$\Rightarrow 1.86\times \frac{0.1}{0.513}=0.3625$

$\Delta T_f=T_0-T_s$

$0.3625=0-T_s$

$\therefore$ freezing point is ${0.362}^{0}C$