Question

The molarity of sulphuric acid is 0.8M and its density is 1.06g/cm3. What will be the concentration of solution in terms of molality and mole fraction?

Answer 1

Since molarity of the solution is 0.8 M, it means the solution have 0.8 moles of H2SO4 in 1000 ml of solution.

Mass of 1000 ml of solution = density x volume = 1.06 g cm-3 x 1000 cm-3 = 1060 g

Mass of H2SO4 in 0.8 mol of H2SO4 = 0.8 mol x 98 g mol-1 = 78.4 g

Mass of water (solvent) = 1060 g - 78.4 g = 981.6 g

Moles of water (solvent) = 981.6 g / 18 g mol-1 = 54.53 mol
Since, molality is the moles of solute in 1 Kg of the solvent, the molality of the solution is = (0.8 mol / 981.6 g) x 1000 g = 0.815 m


mole fraction of H2SO4 = (0.8) / (0.8+54.53) = 0.0145

mole fraction of water = (54.53) / (0.8+54.53) = 0.985