The decomposition of hydrogen peroxide in aqueous solution is often studied in the…
CHEMISTRY · Multi-part · CBSE · Chemistry · Chemical Kinetics · Chemical Kinetics
Problem
The decomposition of hydrogen peroxide in aqueous solution is often studied in the presence of iodide ion.
Experimental chemists have proposed the following elementary steps that occur in acidic solution (aq):
1. H2O2+I−→H2O+IO−
2. H2O2+IO−→H2O+O2+I−
Assume the two steps listed above represent a complete mechanism.
Answer the following questions about the proposed mechanism.
(a) Derive the overall balanced chemical equation for the reaction by summing the elementary steps and canceling any species that appear on both sides.
(b) Identify every species that is (i) an intermediate and (ii) a catalyst in this mechanism. For each species you identify, justify your classification based on how it appears in the elementary steps and the overall equation.
(c) Explain why the presence of iodide ion speeds up the rate of hydrogen peroxide decomposition even though the iodide ion concentration remains nearly constant throughout the reaction.
(d) If the initial concentration of iodide ion is doubled while all other initial concentrations are held constant, qualitatively predict how the initial rate of oxygen formation will change. Justify your prediction in terms of the rate-determining step and the role of the catalyst.