Q24 / 160 · AP EAMCET 2022 (06 Jul Shift 2) · Chemistry

The freezing point depression of a solution containing $0.6 \mathrm{~g}$ of urea (molar mass $=60 \mathrm{~g} \mathrm{~mol}^{-1}$ ) in $100 \mathrm{~mL}$ of benzene (in $\mathrm{K}$ ) is $\left(K_f\right.$ of $\mathrm{CH}_3 \mathrm{COOH}=4.0 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$ )

  • A
    0.30
  • B
    0.58
  • Correct answer
    C
    0.40
  • D
    0.24

Solution

Given, Mass of urea $=0.6 \mathrm{~g}$ Molar mass of urea $=60 \mathrm{~g} \mathrm{~mol}^{-1}$ $K_f$ of benzene $=4.0 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$ and $100 \mathrm{~mL}$ benzene $=0.1 \mathrm{~L} \approx 0 . \mathrm{kg}$ $$ \Delta T_f=K_f m $$ So, $\Delta T_f=4 \times \frac{0.6}{60} \times \frac{1}{0.1}=0.4$

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

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