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Sunday, September 26, 2010

what is volume of hydrogen peroxide means?

ini soalan yang cikgu Zuraifah tanya the other day.

listed here is the answer

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 H2O2 in volumes is given, its percentage strength can be calculated as follows:
For example, we have a sample of H2O2 marked as 30 volume. Then, by definition of '30 volumes H2O2 means that 1 volume of this grade H2O2 gives 30 volumes of O2 at NTP.
So, 1 litre of 30 volume H2O2 gives 30 litre of oxygen at NTP
Strength of hydrogen peroxide solution
From the equation, 2 H2O2 g 2H2O + O2 We find that, 1 mol of O2 = 2 mol of H2O2
Thus, 30 volume H2O2 contains 2.678 mol per litre of this solution. Therefore the Molarity of 30 volume sample of H2O2 = 2.678
So, the strength of H2O2in the 30 volume sample = Molarity x Molar mass = 2.678 x 34 g L-1 = 91.1g/L = 9.11%
'30 volume' sample of H2O2 actually contains 9.11% of H2O2

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