Question

A 1.00 g sample of a hydrogen peroxide (H2O2) solution is placed in an Erlenmeyer flask and diluted with 20 mL of 1 M aqueous sulfuric acid. To this solution is added 0.0200 M KMnO4 solution via a buret, until a pale purple color persists. This requires 22.50 mL of KMnO4 solution. What is the percent by mass of hydrogen peroxide in the original solution?

Answer 1

Following reaction is involved in present system:

2KMnO4  +  5H2O2 +  3H2SO4 →  2MnSO4    +     K2SO4  + 5O2  +   8H2O

From the above balance reaction, it can be seen that 2 moles of KMnO4 is consumed for every 5 moles of H2O2.

 Now, percent by mass of hydrogen peroxide in the original solution can be estimated as follows:
percent by mass = $\frac{\text{mass of H2O2(g)}}{\text(volume of H2SO4(ml))}X 100$
∴percent by mass = $\frac{\text{1}}{\text(25)}X 100$
                             = 4 %