The density of 4% (w/v) NaOH solution is 1.02 g/ml. What is the molality of the solution ?

Explanation

4% (w/v) NaOH solution contains 4g of NaOH is 100ml of the solution.
density of the solution = 1.02 g/ml
`therefore` wt of the solute in 100 ml of the solution = 4g
wt of 100 ml of the solution = 100 x 1.02 = 102 g
Wt. of solvent = Wt of solution - Wt of solute
=102-4=98 g
`therefore` Molarity = `(W/(G.M.W))_"Solute" xx 1000/"wt of solvent in gms"`
`=4/40xx1000/98`=1.02 m