Calculate the mass of urea `(NH_(2)CONH_(2))` required in making `2.5 kg `of `0.25 `molal aqueous solution.

Options

A. 37 g
B. 35 g
C. 34 g
D. 32 g

Answer

a

Explanation

Mass of solvent = 1000 g
Molar mass of urea `(NH_(2)CONH_(2)) = 60 g mol^(-1)`
`0.25` mole of urea `= 0.25xx60 = 15g`
Total mass of solution `= 100 + 15 = 1.015 kg`
1.015 kg of solution contain urea `= 15 g`
2.5 kg of solution `= (15)/(1.015)xx2.5 = 37 g`