Calculate % by mass of a H ₂ O ₂ solution that is 67.2% by volume.

Step-by-step solution

The volume strength of 67.2 corresponds to the volume of oxygen gas produced at STP from 1 L of H ₂ O ₂ solution. The relationship between volume strength ( V ) and molarity ( M ) is given by V = M 11.2 . 67.2 = M 11.2 implies M = 6 . 1 L of 6 M solution contains 6 mol of H ₂ O ₂ , with molar mass 34.016 g/mol. The mass of solute is therefore 6 34.016 = 204.096 g. Assuming a density of 1 g/mL for the aqueous solution, the mass of 1 L is 1000 g. The percentage by mass is 204.096 1000 100 = 20.4096 % , which rounds t