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

Explanation

0.25 molal solution means 0.25 moles of urea in 1000 g of water.
Mass of urea `= 0.25 xx 60 = 15 g`
Total mass of solution `= 1000 + 15 = 1015 g`
or `" " = 1.015 kg`
1.015 kg 1.015 kg of solution contain urea - 15 g
2.5 kg f solution will require urea ` = (15)/(1.015) xx 2.5`
=36.94g