Question

If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution, the change in freezing point of water $\left(\Delta T_{f}\right)$, when $0.01\, mol$ of sodium sulphate is dissolved in $1\, kg$ of water, is $(K_f = 1.86\, K\, kg\, mol^{-1})$

• A. $0.0372\, K$
• B. $0.0558\, K$
• C. $0.0744 \,K$
• D. $0.0186\, K$

Answer 1

Answer: (B)

$0.0558\, K$

Answer 2

Vant Hoff?s factor (i) for $Na_2SO_4 = 3$ $\therefore \Delta T_{f} = \left(i\right) k_{f} \,m$ $= 3\times1.80\times \frac{0.01}{1} = 0.0558 \,K$