Question

0.6 g of an organic compound when dissolved in 21.7 g water freezes at 272.187 K. The molar mass of the organic compound is close to:
($K_f$ of water is 1.86 deg/molality; freezing point is 273 K)

• A. 61 g $mo{l}^{-1}$
• B. 63 g $mo{l}^{-1}$
• C. 65 g $mo{l}^{-1}$
• D. 67 g $mo{l}^{-1}$

Answer 1

The correct option is B 63 g $mo{l}^{-1}$

we have,

$\Delta T_f=K_f\times m$

$273-272.187=1.86\times \frac{0.6}{M\times 21.7}\times 1000$

$M=63gmo{l}^{-1}$

Hence, option (B) is correct.