Decomposing Hydrogen Peroxide

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The purpose of this experiment is to gain an understanding of factors which influence the rates of reactions. Several experiments will be conducted using various combinations of concentrations of the reactant (hydrogen peroxide) and a catalyst (potassium iodide), as well as one pairing in which a change in temperature is the only variable. Data collected will be used to determine the rate law, rate constant, and activation energy for each of the reactions Hydrogen peroxide (H_2 O_2) naturally decomposes into water (H_2 O) and oxygen gas (O_(2 )) according to the following balanced equation.

2 H_2 O_2 (aq) ↔ 2 H_2 O (l)+O_(2 ) (g)

Normally this reaction takes a long period of time, but the rate of reaction can be increased with the addition of a catalyst, which lowers the activation energy needed for a reaction to begin, but is not consumed in the reaction. In this experiment, potassium iodide (KI) will be used:

2H_2 O_2 (aq) □( □(↔┴KI )) 2 H_2 O (l)+O_(2 ) (g)

It is expected that the reaction will not occur at a significant rate until the addition of the catalyst.

The rate of a reaction can be expressed as the change in concentration of either reactants or products divided by the change in time, and will decrease as the reaction progresses(Chang 558).

rate= -1/2 (∆ [H_2 O_2])/(∆ t)= 1/2 (∆ [H_2 O])/(∆ t)= (∆ [O_2])/(∆ t)

A reaction’s rate is proportional to the concentration of the reactant, and the value of this ratio (called the rate constant, k) remains the same throughout the reaction, regardless of concentration. Only a change in temperature will change the rate constant for a given reaction. It is hypothesized that an increase in temperature will result in an increase in the value of ...

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...f just H2O2 without the catalyst as a negative control may have provided concrete data for comparison in the rates of reaction, supporting the hypothesis that the catalyst would initiate the reaction


In completing this experiment I gained a better practical understanding of the effects of temperature, concentration, and catalysts on rates of reaction. A solid understanding of how catalysts function, especially in biological systems as enzymes, will serve me well when I am a physician assistant. Chemical reactions are taking place all around us; the realization of how occur and how they can be manipulated will be of benefit in many ways, from maintaining safe pool water, to making gravy, to coloring hair…better understanding will lead to success.

Works Cited
Chang, Raymond. Chemistry. Boston: McGraw-Hill Higher Education Publishing, 2009.
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