Q23 / 160 · TS EAMCET 2022 (20 Jul Shift 1) · Chemistry

The freezing point of equimolal aqueous solution will be highest for

  • A
    $\mathrm{C}_6 \mathrm{H}_5-\mathrm{NH}^{\mathrm{N}} \mathrm{H}_3 \stackrel{-}{\mathrm{C}} \mathrm{l}$
  • B
    $\mathrm{Ba}\left(\mathrm{NO}_3\right)_2$
  • C
    $\mathrm{LaCl}_3$
  • Correct answer
    D
    $\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6$

Solution

Depression in freezing point $\Delta \mathrm{T}_{\mathrm{f}}=\mathrm{iK}_{\mathrm{f}} \mathrm{m}$. $$ \mathrm{i}=\frac{\text { Total no. of moles of particles after dissociation / association }}{\text { No. of moles of particles before dissociation / association }} $$ Now, $\mathrm{C}_6 \mathrm{H}_5 \mathrm{NHN}^{+} \mathrm{H}_3 \mathrm{Cl}^{-}, \mathrm{Ba}\left(\mathrm{NO}_3\right)_2, \mathrm{LaCl}_3$ produces 2, 3 and 4 moles of ions after dissociation, respectively. Hence, depression in freezing point will be gradually increasing only $\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6$ does not dissociate in aqueous solution. Therefore, it's solution will have the highest freezing point.

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

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