Question

One brand of laundry bleach is an aqueous solution containing 4.00% sodium hypochlorite (NaOCl) by mass
What is the molarity of this solution? (Assume a density of 1.02 g/mL .)

Answer 1

The question tells us that the concentration of the solution is 4.00% w/w.
That is 100 g of the solution contains 4.00 g NaOCl.
or
That is 1000 g of the solution contains 40.0 g NaOCl

The volume occupied by 1000 g is
mass/density
1000g/1.02 g ml^-1 = 980.4 ml

Molar mass of NaOCl is 74.44 g/mol

Number of moles of NaOCl is

40.0 g/74.44 g/mol = 0.5373 mole

so molarity is

moles/volume =

Answer 2

.54804