Q24 / 180 · KCET 2015 · Chemistry

Which of the following aqueous solution has the highest freezing point?

  • A
    \( 0.1 M \) Sucrose
  • Correct answer
    B
    \( 0.01 \mathrm{MNaCl} \)
  • C
    \( 0.1 \mathrm{MN} \mathrm{ACl} \)
  • D
    \( 0.01 \mathrm{MN} a_{2} \mathrm{SO}_{4} \)

Solution

Depression in freezing point, \( \Delta T_{f}=i K_{f} m \) \(\Delta T_{f} \) will depends on van't Hoff factor. \(\begin{array}{|l|l|l|l|} \hline \text{Compounds} & \text{Concentration} & \text{van't Hoff factor (i)} & \boldsymbol{\Delta} T_boldsymbol{f} \\ \hline \text{Sucrose} & 0.1 \mathrm{M} & 1 & 0.1 K_{f} \\ \hline \mathrm{NaCl} & 0.01 \mathrm{M} & 2 & 0.02 K_{f} \\ \hline \mathrm{NaCl} & 0.1 \mathrm{M} & 2 & 0.2 K_{f} \\ \hline \mathrm{Na}_{2} \mathrm{SO}_{4} & 0.01 \mathrm{M} & 3 & 0.03 K_{f} \\ \hline \end{array}\) Therefore, depression in freezing point follow the order: \(0.1 \mathrm{MNaCl}_{i=2}>0.1 \mathrm{M} \text { Glucose }>0.01 \mathrm{MN}_{i=1} \underset{i=3}{\mathrm{~N}} \mathbf{S O}_{4}>0.01 \mathrm{MNaCl}_{i=2}\) Depression in freezing point is minimum in case of \( 0.01 \mathrm{M} \mathrm{NaCl} \) solution, hence, it will have maximum freezing point.

Hence, the correct answer is option: 'B'.

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