We know, molar mass of H₂O₂ is 34gm. According to this reaction, 2 moles of peroxide is involved, so mass becomes 68gm.

Also, we know that 1mole of any gas occupies a volume of 22.4L at NTP.

Now, 5 volume H₂O₂ solution means that 1 L of 5 volume H₂O₂ on decomposition gives 5L of O₂ at NTP.

So we can see from the reaction that, from 22.4L at NTP, we get 68gm H₂O_2.

Now to get the required 5L of O₂ at NTP, we need () gm H₂O₂

= 15.179gm

But we know that 5L of O₂ at NTP is produced from 1L of 5 volume H₂O_{2 ,} as we have to find strength of 5 volume H₂O₂

∴ Strength of H₂O₂ in 5 volumes of it is 15.179gm/L

∴ Percentage strength = ()%

= 1.518%