Question

The concentrated sulfuric acid we use in the laboratory is 98.0 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

Consider 1 L = 1000 mL of solution

Mass of solution = volume x density

= 1000 x 1.83 = 1830 g

Mass of H2SO4 = 98.0/100 x 1830 = 1793.4 g

Moles of H2SO4 = mass/molar mass of H2SO4

= 1793.4/98.08 = 18.3 mol

Molarity = moles of H2SO4/volume of solution in L

= 18.3/1 = 18.3 M

Mass of water = 1830 - 1793.4 = 36.6 g = 0.0366 kg

Molality = moles of H2SO4/mass of water in kg

= 18.3/0.0366

= 500 mol/kg = 500m