Question

An aqueous solution boils at ${101}^{\circ }C$. What is the freezing point of the same solution?
(Given :$K_f={1.86}^{\circ }C/m$ and $K_b={0.51}^{\circ }C/m$)

• A. ${3.647}^{\circ }C$
• B. $-{3.647}^{\circ }C$
• C. $-{0.364}^{\circ }C$
• D. None of these

Answer 1

The correct option is B $-{3.647}^{\circ }C$

(b) $m=\frac{\Delta T_b}{K_b}\Rightarrow \frac{1}{0.51}=\frac{\Delta T_f}{K_f}$
$\Rightarrow \frac{1}{0.51}=\frac{\Delta T_f}{1.86}$
$\Delta T_f=3.647$ or $T_f=-{3.647}^{\circ }C$