Question

A 40% hcl solution is found to have a density of 1.20 g/ml.Calculate the molarity of the solution.

Answer 1

Assume you have 1.00 L (1000 mL) of solution.

d = m / V

m = d x V = 1.23 g/mL x 1000 mL = 1230 g of solution

0.387 mol/L x 1 L = 0.387 mol HCl

0.387 mol HCl x (36.5 g / 1 mol) = 14.1 g HCl

mass of water = 1230 g solution - 14.1 g HCl = 1216 g H2O = 1.216 kg H2O

molality = mol HCl / kg water = 0.387 mol / 1.216 kg = 0.318 mol/kg (or 0.318 molal)