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 1.83g/mL

Answer 1

Consider 1 L = 1000 mL of solution

Mass of solution = volume x density

Mass of solution $= 1000 × 1.83 = 1830 g$

Mass of $H_2SO_4 =\frac{ 98.0}{100} × 1830 = 1793.4 g$

Moles of H2SO4 = mass/molar mass of H2SO4

$=\frac{ 1793.4}{98.08} = 18.3 moles$

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

$= \frac{18.3}{0.0366} = 500 mol/kg = 500M$