If 50 % of 1 M Na ₂ SO ₄ is dissociated in aqueous solution of density 1.2 ~g ~mL ⁻¹ , what is the molality of Na ⁺ ion in the solution?

Step-by-step solution

Density (d) of solution =1.2 ~g / ml 1 ~mol Na ₂ SO ₄ 2 ~mol 2 Na ⁺ + SO ₄²⁻ MW of Na ₂ SO ₄=142 ~g / mol 50 % dissociation of Na ₂ SO ₄ produces 1 ~mol of Na ⁺ 1( M ) Na ₂ SO ₄ solution has 1( M ) Na ⁺ ions in 1000 ml solution =1200 ~g solution. Weight of solvent =(1200-142)=1058 ~g The molality of Na ⁺ ion = 1 1000 1058 =0.95 ~m