Question

A solution contains 410.3 g of H₂SO₄ per litre of the solution at 20°C. If its density is 1.243 g cm⁻³, what will be its molality and molarity?

Answer 1

Given: Mass of H₂SO₄ = 410.3 g per litre of solution

Density of solution = 1.243 g/cm³ = 1243 g/L

Mass of solvent = 1243 − 410.3 = 832.7 g = 0.8327 kg

Molar mass of H₂SO₄ = 98 g/mol

Molarity (M) = `"Mass of solute (g)"/("Molar mass" xx "Volume in L")`

= `410.3/(98 xx 1)`

= 4.187 mol/L

Molality = `"Moles of solute"/"Mass of solvent in kg"`

= `4.187/0.8327`

= 5.027 mol/kg

∴ The molarity of the solution is 4.19 M and molality is 5.027 mol/kg.