Answer to Question #302334 in General Chemistry for Donna

Question

A solution of hydrogen peroxide, H2O2, is 30.0% by mass and has a density of 11110g/L solution. Calculate the (a) molality, (b) molarity, and (c) mole fraction.

Answer 1

Assume that the mass of H₂O₂ solution is 100 g.

Thus:

Mass of H₂O₂ = (%H₂O₂ × Mass of solution) / 100% = (30.0% × 100 g) / 100% = 30.0 g

Moles of H₂O₂ = Mass of H₂O₂ / Molar mass of H₂O₂ = 30.0 g / 34.0147 g mol^-1 = 0.88197 mol

Solution volume = Mass of solution / Density of solution = 100 g / 1.135 g cm^-3 = 88.1057 cm^-3

Solution volume = 88.1057 cm^-3 = 88.1057 mL = 0.088106 L

Molarity of H₂O₂ = Moles of H₂O₂ / Solution volume

Molarity of H₂O₂ = 0.88197 mol / 0.088106 L = 10.01 mol/L = 10.0 M

Molarity of H₂O₂ = 10.0 M

OR (short form solution):

(1.135 g soln/1 mL soln) × (30 g H₂O₂/100 g soln) × (1 mol H₂O₂/34 g H₂O₂) × (1000 mL/1 L) = 10.0 M

Answer: The molarity of a 30.0% hydrogen peroxide solution is 10.0 M.