Convert a 4.7% mass percent (mass-to-volume percent ) solution of NaOCl (formula mass = 74.441 g/mol) to molarity. Assume the density of the solution is 1.0 g/mL.

Answer 1

4.7% (mass/volume) = 4.7 g NaOCl / 100 mls = 47 g NaOCl / 1000 mls (1 L)

molar mass NaOCl = 74.44 g / mol

Molarity (M) = moles / liter.

M = 47 g / L x 1 mol / 74.44 g = 0.63 M (2 sig. figs.)

We don't need to use the density unless we want to calculate the molality (m) of the solution, which is given as moles NaOCl / kg water.