22.4 vol H2O2 means 1mL of H2O2 solution gives 22.4mLO2 2H2O2⟶2H2O+O2 2 mol 1 mol 68g 22400mL at NTP ∴22400mLO2 is obtained by 68gH2O2 ∴22.4mLO2 is obtained by
68×22.4
22400
=0.068gH2O2 or 1mLH2O2 solution =0.068g ∴100mLH2O2 solution =0.0680×100=6.8%