10 volume solution of H2O2 means that 1L of this H2O2 will give 10 L of oxygen at STP
2H2 O2 ( l) → O2( g) +2 H2O( l)
2×34 g 22.4 L at STP
22.4 L of O2 at STP is produced from H2O2 = 68 g
20 L of O2 at STP is produced from H2O2 =68X20/22.4 = 60.72 g
Therefore, strength of H2O2 in 20 volume H2O2 = 60.72 g/L