Question

A solution of $0.450g$ of urea $(mol.wt.60)$ in $22.5g$ of water showed ${0.170}^{\circ }C$ of elevation in boiling point, the molal elevation constant of water:

• A. $0.51$
• B. $0.95$
• C. $0.25$
• D. $2.25$

Answer 1

The correct option is A $0.51$

Relation between elevation in boiling point and molal elevation constant is as follows.

$\Delta T_b=K_b\times \frac{wt.ofsolute}{mol.wtofsolute}\times \frac{1000}{wt.ofsolventingrms}$

$0.170=K_b\frac{0.450}{60}\times \frac{1000}{22.5}{K}_b=0.51$

So answer is A.