Question

Q.63
If molality of urea in an aqueous solution is 5 then the mass
percentage of urea in the solution will be nearly
Choose answer:
30%
23%
27%
20%

Answer 1

Answer:

it would be 27 or 30

Explanation:

percent

Answer 2

Answer:

23%

Explanation:

Molality is defined as the moles of the solute present in 1 kilogram of the solvent.

Given that :  Molality = 5

It means that 5 moles of urea are present in 1 kg of the solvent.

Molar of urea = 60.06 g/mol

The formula for the calculation of moles is shown below:

$moles = \frac{Mass\ taken}{Molar\ mass}$

Thus,

$5\ moles= \frac{Mass}{60.06\ g/mol}$

Mass = 300.3 g

Mass of the solute =  300.3 g

Mass of the solvent = 1 kg = 1000 g

Total mass = 1300.3 g

Thus, Mass % = 300.3 g/1300.3 g *100 = 23%