Question

If a solution of NaOH has a 20% mass percent of NaOH and a density of 1.22 g/ml, what is the molarity of this solution ?

Answer 1

Answer –

We are given, 20% mass percent of NaOH , density = 1.22 g/mL

So, 20% mass percent of NaOH means 20 g of NaOH in 100 g of solution

So, moles of NaOH = mass of NaOH / molar mass of NaOH

                                 = 20 g / 39.9969 g.mol^-1

                                 = 0.500 moles of NaOH

Now we need to convert 100 g od solution to volume

We know,

Density = mass / volume

So, volume = mass / density

                  = 100 g / 1.22g.mL^-1

                = 81.97 mL

So, molarity of solution = 0.500 mole / 0.08197 L

                                  = 6.1 M

So, molarity of this solution is 6.1 M