Question

what is the mole fraction of solute in aqueous solution of 30% NAOH?

Answer 1

Let us assume the whole mass of the solution to be 100 g. 30 % NaOH of 100 g of the solution is 30 g. This implies that 70 g left over is the mass of water in the solution.

So let's calculate the moles first.

NaOH = 23 + 16 + 1 = 40 g

Given Mass = 30 g

=> Moles = 30 g / 40 g = 0.75 moles

H₂O = 18 g

Given Mass = 70 g

=> Moles = 70 / 18 = 3.88

Therefore Mole fraction of solute ( NaOH ) =

Moles of NaOH / Sum of moles of NaOH + Number of Moles of H₂O

=> Mole fraction = 0.75 / 0.75 + 3.88

=> Mole fraction = 0.75 / 4.63

=> Mole fraction of NaOH = 0.16

Hence mole fraction of the solute is 0.16.

Hope it helps !