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## Strength of hydrogen peroxide solution

It is customary to indicate the strength of a sample of hydrogen peroxide solution in terms of the 'volume of oxygen at NTP that one volume of hydrogen peroxide gives on heating'. When the grade of H_{2}O

_{2}in volumes is given, its percentage strength can be calculated as follows:

For example, we have a sample of H

_{2}O

_{2}marked as 30 volume. Then, by definition of '30 volumes H

_{2}O

_{2}means that 1 volume of this grade H

_{2}O

_{2}gives 30 volumes of O

_{2}at NTP.

So, 1 litre of 30 volume H

_{2}O

_{2}gives 30 litre of oxygen at NTP From the equation, 2 H

_{2}O

_{2}g 2H

_{2}O + O

_{2}We find that, 1 mol of O

_{2}= 2 mol of H

_{2}O

_{2}

Thus, 30 volume H

_{2}O

_{2}contains 2.678 mol per litre of this solution. Therefore the Molarity of 30 volume sample of H

_{2}O

_{2}= 2.678

So, the strength of H

_{2}O

_{2}in the 30 volume sample = Molarity x Molar mass = 2.678 x 34 g L

^{-}

^{1}= 91.1g/L = 9.11%

'30 volume' sample of H

_{2}O

_{2}actually contains 9.11% of H

_{2}O

_{2}

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