Question

An old sample of concentrated sulfuric acid to be used in the laboratory is approximately 98.1 percent h2so4 by mass. calculate the molality and molarity of the acid solution. the density of the solution is 1.83 g/ml.

Answer 1

Basis: 100 mL solution

From the given density, we calculate for the mass of the solution.

                        density  = mass / volume
                        mass = density x volume

                       mass = (1.83 g/mL) x (100 mL) = 183 grams

Then, we calculate for the mass H2SO4 given the percentage.
                   
                      mass of H2SO4 = (183 grams) x (0.981) = 179.523 grams

Calculate for the number of moles of H2SO4,
                  moles H2SO4 = (179.523 grams) / (98.079 g/mol)
                        moles H2SO4 = 1.83 moles

Molarity:
                     M = moles H2SO4 / volume solution (in L)
                         = 1.83 moles / (0.1L ) = 18.3 M

Molality:
                     m = moles of H2SO4 / kg of solvent
                        = 1.83 moles / (183 g)(1-0.983)(1 kg/ 1000 g) = 588.24 m