10 volume H2O2 means 1 mL H2O2 solution produces 10 mL O2 at STP 2H2O2 → 2H2O + O2 22400 mL O2 at STP is produced from 68 g. H2O2 ∴ 10 mL O2 is produced from
68×10
22400
g = 0.03036 g H2O2 ∴ 1 mL H2O2 solution contains 0.03 g H2O2 (approx.) ∴ 100 mL H2O2 solution contains 0.03 × 100 = 3 g H2O2 (approx.)