Correct Answer - B
20 volumes of `H_(2)O_(2)` means 20 litres of oxygen is obtained at STP by the decomposition of 1 litre `H_(2)O_(2)` solution
`{:(2H_(2)O_(2),to,2H_(2)O+,O_(2)),(2 "mole",,,1 "mole"),(68 g,,,22*4 "litre at" STP):}`
`22*4` litres oxygen is obtained from 68 g `H_(2)O_(2)`
`:.` 20 litres oxygen is obtained from
`=(68)/(22*4)xx20=60*7 g H_(2)O_(2)`
`:.` 1000 ml of `H_(2)O` solution contains `60*7` g `H_(2)O_(2)`
100 ml `(~~100 g)` solution contains `(60*7)/(1000)xx100`
`:.` Strength of `H_(2)O_(2)` solution
`=6*07 g H_(2)O_(2)=6*07%`
