Question

The freezing point of one molal NaCl solution assuming NaCl to be 100% dissociated in water(molal depression constant = 1.86) :

• A. -2.72$^\circ$C
• B. -3.72$^\circ$C
• C. 2.72$^\circ$C
• D. 3.72$^\circ$C

Answer 1

Answer: (B)

For $NaCl \,i=2$
$\Delta T_{f}=2 K_{f} m$
$=2 \times 1.86 \times 1=3.72$
$T_{s}=T-\Delta T_{f}$
$=0-3.72=-3.72{ }^{\circ} C$