An aqueous solution of urea (molar mass 60 g/mol ) has a density of 1.12 g/mL and a molarity of 2.5 M . Calculate the molality of the solution. (Report your answer by multiplying the molality by 10 an

Question

An aqueous solution of urea (molar mass 60 g/mol ) has a density of 1.12 g/mL and a molarity of 2.5 M . Calculate the molality of the solution. (Report your answer by multiplying the molality by 10 and rounding to the nearest integer).

TestHub · Accepted Answer

To find molality, assume 1 L of solution.

Moles of urea = $2.5 m o l$ .

Mass of urea = $2.5 m o l \times 60 g / m o l = 150 g$ .

Mass of solution = $1000 m L \times 1.12 g / m L = 1120 g$ .

Mass of solvent = $1120 g - 150 g = 970 g = 0.970 k g$ .

Molality = $2.5 m o l /0.970 k g \approx 2.577 m o l / k g$ .

$2.577 \times 10 \approx 25.77$ , which rounds to 26.

Chemistry - Concentration Terms Question with Solution | TestHub

Doubts & Discussion

JEE Main 2028 (Class 11)