Question

Mass percentage of urea in aqueous solution is 30%.The molality of urea in the solution is:
(Mol. wt. of urea = 60 g mole${}^{-1}$)

• A. 5.2 m
• B. 7.1 m
• C. 6.1 m
• D. 4.5 m

Answer 1

The correct option is B 7.1 m

$Molality=\frac{Wt}{GMWt}\times \frac{1000}{Wtofwater}$

Weight of Water is $100-30=70g$

$Molality=\frac{30}{60}\times \frac{1000}{70}$ = $7.1m$