Question

Molality of $30\%$ (w/w) urea solution is:

• A. $0.357$
• B. $3.57$
• C. $0.714$
• D. $7.14$

Answer 1

The correct option is D $7.14$

30% $\left(\omega /\omega \right)$ means 30 gm urea in 100 gm solution.

So, weight of solvent $=100-30=70$ gm

Molality $=\frac{massofsolute}{M.\omega t}\times \frac{1000}{massofsolvent\left(Kg\right)}$

$=\frac{30}{60}\times \frac{1000}{70}$

$=7.14molal$