Question

20 vol H2O2 nearly......%H2O2

Answer 1

Let us take 1 liter of H2O2 and let it decompose:

20 liters of O2 is 20/22.4 = 0.893 moles of O2.

To get 0.893 moles of O2, you must have started with 2 x 0.893 = 1.786 moles of H2O2

Which weighs 60.7 grams.

Answer is Approx 6%