Question

Which observable property is used in the kinetic study of the following first order reaction and why?

\[\ce{H2O2_{(aq)} ->[Pt] H2O_{(l)} + \frac{1}{2} O2_{(g)}}\]

Answer 1

1. In the kinetic study of the first-order decomposition of hydrogen peroxide \[\ce{H2O2_{(aq)} ->[Pt] H2O_{(l)} + \frac{1}{2} O2_{(g)}}\] volume of oxygen gas (O₂) evolved is the observable property used.
2. As the reaction proceeds, oxygen gas is liberated, which can be collected and measured over time.
3. The amount of O₂ evolved is directly proportional to the amount of hydrogen peroxide decomposed.
4. Hence, by measuring the volume of O₂ collected at different time intervals, the concentration of H₂O₂ at time t can be indirectly determined.
5. This allows application of the first-order integrated rate law to calculate the rate constant k and verify the order of the reaction.