If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution,…

If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution, the change in freezing point of water $\left(\Delta \mathrm{T}_{\mathrm{f}}\right)$, when $0.01 \mathrm{~mol}$ of sodium sulphate is dissolved in $1 \mathrm{~kg}$ of water, is $\left(\mathrm{K}_{\mathrm{f}}=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\right)$
  1. $0.0372 \mathrm{~K}$
  2. $0.0558 \mathrm{~K}$
  3. $0.0744 \mathrm{~K}$
  4. $0.0186 \mathrm{~K}$

Solution

Vant Hoff's factor (i) for $\mathrm{Na}_2 \mathrm{SO}_4=3$ $\begin{aligned} \therefore \Delta \mathrm{T}_{\mathrm{f}}= & \text { (i) } \mathrm{k}_{\mathrm{f}} \mathrm{m} \\ & =3 \times 1.80 \times \frac{0.01}{1}=0.0558 \mathrm{~K} \end{aligned}$

Asked in: MHT CET Full Test 4

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