Hydrogen peroxide slowly decomposes on its own into oxygen gas and water. 2 H2O2 (aq) → 2 H2O (l) + — Kinetics and Catalysis Chemistry Question

An excellent response included:

Experimental Plan: A well designed experimental plan that indicated that the volume of hydrogen peroxide used in each trial was held constant and that the amount of the catalyst was equal in each trial. Also indicated in the plan was how the volume of hydrogen peroxide and the amount of catalyst used was determined. The plan also indicated what was being measured, i.e., the number of bubbles, the time until the reaction stopped, the change in temperature, etc. and how that quantity would be measured.

Data and Observations: Data and observations collected were organized in a table format with proper units. Also present in the data table was the volume of hydrogen peroxide and amount of catalyst used in each trial. The data showed multiple trials of each catalyst and was precise. Along with the data collected, there were many, good qualitative observations that could be used to support the ranking along with the quantitative observations.

Analysis and Conclusions: The conclusions drawn included the ranking of the catalysts agreeing with the data collected and a discussion of how the observations and data supported that ranking, e.g. "Yeast produced the greatest number of bubbles so it was the most effective catalyst." An excellent response also included some discussion of the chemistry involved in the experiment, i.e. "A catalyst is a substance that speeds up the rate of a reaction usually by lowering the activation energy without itself being used up in the reaction. For example, for the reaction:
2 H₂O₂ (aq) → 2 H₂O (l) + O₂ (g), the process occurs very slowly. However the addition of KI provides for an alternate reaction pathway with lower activation energy so the decomposition occurs faster according for this pathway:
H₂O₂ + I^- (aq) → IO^- (aq) + H₂O (l) and
IO^- (aq) + H₂O₂ → I^- (aq) + H₂O + O₂.
The second reaction regenerated the I^- which therefore acts as a catalyst.
The same type of thing happens with the iron III chloride as the Fe³⁺ ion is reduced to Fe²⁺ ion and oxygen gas is formed by the peroxide. The Fe²⁺ is oxidized back to the Fe³⁺ ion in the acidic environment to act as a catalyst.
H₂O₂ + 2 Fe 3+ → 2 H⁺ + O₂ + 2 Fe 2+ and
²Fe²⁺ + H₂O²⁺ 2 → 2 Fe³⁺ + 2H₂O. Yeast is a biological enzyme and thus would increase the rate of decomposition of hydrogen peroxide."