Answer to Question #302338 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

The molar mass of H₂O₂ is 34 g mol^-1.

The molar mass of H₂O is 18 g mol^-1.

Solution:

Assume that 100 g solution is given.

1) Determine the molarity of the solution:

(1.11 g soln / mL soln) × (30 g H₂O₂ / 100 g soln) × (1 mol H₂O₂ / 34 g H₂O₂) × (1000 mL / 1L) = 9.79 M

The molarity of H₂O₂ solution is 9.79 M

2) Determine the mole fraction of H₂O₂:

χ(H₂O₂) = Moles of H₂O₂ / Total moles of solution

Moles of H₂O₂ = (30 g H₂O₂) × (1 mol H₂O₂ / 34 g H₂O₂) = 0.88235 mol

Moles of H₂O = (70 g H₂O) × (1 mol H₂O / 18 g H₂O) = 3.8889 mol

Total moles of solution = Moles of H₂O₂ + Moles of H₂O = 0.88235 mol + 3.8889 mol = 4.77125 mol

χ(H₂O₂) = 0.88235 mol / 4.77125 mol = 0.18493 = 0.185

The mole fraction of H₂O₂ is 0.185