Question

30% of NaOH solution has density 1.20 g/ml. Calculate its molality and molarity.​

Answer 1

First thing is to convert w/v% to w/w % NaOH

Density is 1.2g/ml so in 100 ml it will be 120g total weight

30% w/v so in 100g will be 30g NaOH

so weight of water = 120–30g = 90g water.

Therefore 30g per 120g

so 30/40 moles = 0.75moles per 90g

so 0.75/90 x 1000g = Molality

so 8.33 moles per Kg = molality of NaOH