Question

the molality of 4% NaOH solution having density 1.02g/ml is

Answer 1

4% means 0.4 M NaOH

0.4 moles NaOH is present in 1000 ml solution

Wt. of solute NaOH = 40 * 0.4

Wt. of solute NaOH =  16

Wt. of solution = v * d

= 1000 * 1.02

= 1020

Wt. of solvent = (1020 - 16) gm H2O

Molality = 0.4 * (1000 /  (1020 - 16 ))

Molality = 0.4 mol