What is the molality of 40% (by mass) urea solution?

11.11

40% (by mass) urea solution means 40 g urea is present in 100 g solution.

Mass of solvent = 100 - 40 = 60g

Molecular mass of urea (NH2CONH2) = 60 g/mol

No of moles of urea = \(\frac{40}{60}\) = \(\frac{2}{3}\)

Molality = \(\frac{\text{no of moles of solute}}{\text{Mass of solvent(in g)}}\) x 1000 = \(\frac{2}{3 × 60}\) x 1000

m = \(\frac{100}{9}\) = 11.11