The density of 2 M aqueous solution of NaOH is 1.28 g/cm3. The molality of the solution is [Given that molecular mass of NaOH = 40 g mol-1]

Let, volume of solution = 1 litreMole of NaOH = 2Mass of NaOH solution = 1000 × 1.28 = 1280 gMass of H2O = (1280 – 2 × 40) = 1200 g = 1.2 kg Molality (m)= Mole of NaOH Mass of solvent (kg)=21.2=1.67 m