10: Decomposition of Hydrogen Peroxide
- Page ID
- 516594
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)PURPOSE
- To conduct the catalyzed decomposition of hydrogen peroxide under various conditions.
- To determine the rate law expression for the reaction.
- To calculate the rate constant for the reaction.
- To calculate the activation energy for the reaction.
INTRODUCTION
The decomposition of hydrogen peroxide, \( \ce{H2O2} \), in an aqueous solution proceeds very slowly. For instance, a commercial bottle of 3 % hydrogen peroxide is stable for a long duration. The decomposition reaction is described by the equation:
\[ 2\, \ce{H2O2}\, (aq) \rightarrow 2\, \ce{H2O}\, (l) + \ce{O2}\, (g) \]
To accelerate this naturally slow process, several catalysts can be utilized, including potassium iodide (KI), manganese(IV) oxide (MnO2), or the enzyme catalase.
In this experiment, the catalyzed decomposition of hydrogen peroxide is carried out in a closed vessel. By doing so, the reaction rate can be determined by monitoring the pressure increase that occurs as oxygen gas (O2) is produced.
This approach allows for several calculations and determinations:
- The rate constant for the reaction can be calculated.
- By varying the initial molar concentration of the hydrogen peroxide solution (as detailed in Parts A, B, and C), the rate law expression for the reaction can be determined.
- By conducting the reaction at different temperatures (such as approximately 20 °C and 30 °C, as detailed in Part D), the activation energy (Ea) for the reaction can be calculated.
Rate Law:
\[ rate = k[\ce{H2O2}]^m[\ce{I-}]^n \]
Initial Rate:
\[ rate = \frac{\Delta[reactant]}{\Delta t} \]
Determining Order:
\[ \frac{rate_1}{rate_2} = \left( \frac{[reactant]_2}{[reactant]_1} \right)^n \]
- 10.1: Decomposition of Hydrogen Peroxide - Experiment
- This page details the safety precautions, equipment, and chemicals necessary for an experiment that decomposes hydrogen peroxide (H2O2) using potassium iodide (KI). It outlines a four-part procedure that varies concentrations of H2O2 and KI, as well as temperatures, while emphasizing safe pressure relief and proper disposal of chemicals. The experiment focuses on data collection regarding the gas pressure produced during the reactions.
- 10.2: Decomposition of Hydrogen Peroxide - Pre-lab
- This page discusses catalysts in chemical reactions, highlighting their ability to lower activation energy and enhance initial reaction rates. It details the decomposition of hydrogen peroxide, investigating pressure buildup in a closed system during the reaction. Furthermore, it includes a practical task for calculating molarity from various concentrations of hydrogen peroxide solution, stressing the need for accurate conversions of mass/volume percentages to molarity in experimental setups.
- 10.3: Decomposition of Hydrogen Peroxide - Data and Report
- This page details an experiment on the catalyzed decomposition of hydrogen peroxide using potassium iodide, including sections for data collection and analysis. It includes tables for documenting reactant details, initial rates, and concentrations. Students perform calculations for pressure to molarity conversions, initial concentrations, rate laws, and the rate constant k. They are also guided to calculate activation energy using the Arrhenius equation.