Question

The increase in boiling point of a solution containing 0.6 g urea in 200 gram water is 0.50$^\circ$C.Find the molal elevation constant

• A. 10 K gram $mol^{-1}$
• B. 1.0 K $mol$
• C. 10 K kg $mol^{-1}$
• D. 10 K kg mol

Answer 1

Answer: (C)

10 K kg $mol^{-1}$

Answer 2

Molality, $m = \frac{0.6}{60} \times \frac{1000}{200}$ = 0.05 m $\Delta \, T_b$ = 0.5 K now $\Delta \, T_b = K_b \times m$ or $K_b = \frac{\Delta \, T_b}{m} = \frac{0.5}{0.05}$ = 10 K kg mol$^{-1}$