All Answers (48) Hydrogen Peroxide is H2O2 with a molar mass of 34.015 g/mole. A 30% solution of H2O2 is 30% H2O2 and 70% H2O by volume. So a liter of this solution contains 0.30 liter of H2O2 and 0.70 liter. of H2O. The density of H2O2 is 1.44 g/cm^3 = 1.44 g / 0.001 liter.