Question

A mixture of 1 g naphthalene ( mol mass 128) and 10 g camphor melts at 147 degree celcius where as pure camphor melts at 177.5 degree celcius. What is cryoscopic constant ( Kf) of camphor

Answer 1

1. The formula of cryoscopic constant:

$∆T_f=K_f\times m$

2. $∆T_f=177.5-147=30.5$

Molality of naphthalene = $\frac{{\displaystyle \frac{1}{128}}}{{\displaystyle \frac{10}{1000}}}=\frac{1}{128}\times \frac{1000}{10}=0.781$

3. K_f = 39 C/m.