8: Redox Reactions
- Page ID
- 516592
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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 investigate the principles of redox reactions by observing the chemical conversion of iron(II) ions to iron(III) ions using various oxidizing agents (such as hydrogen peroxide, potassium permanganate, and sodium hypochlorite) and the reduction of iron(III) ions to iron(II) ions using various reducing agents (such as sodium sulfite, sodium bromide, and sodium iodide).
- To utilize chemical indicators (potassium thiocyanate and potassium ferricyanide) to test for and confirm the presence of iron(III) ions and iron(II) ions, respectively, after redox reactions have occurred.
- To observe and document the characteristic colorful states of manganese (such as Mn2+, MnO2, and MnO4−) corresponding to various oxidation numbers (+2 through +7) and use these visual changes to determine the products of redox reactions and write corresponding balanced half-reactions and overall equations.
INTRODUCTION
- Iron Ion Redox Chemistry (Parts A and B): These experiments involve observing the conversion between iron(II) ions and iron(III) ions. Part A examines the oxidation of Fe2+ to Fe3+ using various oxidizing agents, including hydrogen peroxide (H2O2), potassium permanganate (KMnO4), and sodium hypochlorite (NaClO). Conversely, Part B investigates the reduction of Fe3+ to Fe2+ using reducing agents like sodium sulfite (Na2SO3), sodium bromide (NaBr), and sodium iodide (NaI). The presence of the respective iron ions is confirmed using specific chemical indicators: potassium thiocyanate (KSCN) is utilized to test for Fe3+, and potassium ferricyanide (K3[Fe(CN)6]) is used to test for Fe2+.
- Colorful States of Manganese (Part C): This section focuses on the relationship between oxidation number and visible color for manganese. Reactions are performed involving manganese compounds (such as manganese(II) sulfate and potassium permanganate) to observe and document the characteristic colors corresponding to various oxidation numbers of manganese, which range from +2 (e.g., Mn2+, colorless or light pink) up to +7 (e.g., MnO4−, very dark purple). These observations are then used to analyze and write balanced half-reactions and overall equations for the redox processes.
Manganese occurs in the following oxidation numbers.
|
Oxidation number |
Species |
Color |
|---|---|---|
|
+2 |
\( \ce{Mn^{2+}}\) (aq) |
Colorless or light pink |
|
+3 |
\( \ce{Mn^{3+}}\) (aq) |
Rose or red |
|
+4 |
\( \ce{MnO_{2}}\) (s) |
Dark brown |
|
+5 |
\( \ce{MnO^{3-}_{4}}\) (aq) |
Blue |
|
+6 |
\( \ce{MnO^{2-}_{4}}\) (aq) |
Green |
|
+7 |
\( \ce{MnO^{-}_{4}}\) (aq) |
Very dark purple |
- 8.1: Redox Reactions - Experiment
- This page provides safety precautions for handling caustic substances like hydrochloric and sulfuric acids, along with sodium hydroxide. It details the materials needed for a laboratory experiment and outlines a three-part experimental procedure: Part A investigates iron(II) reactions with oxidizing agents, Part B studies iron(III) reactions with reducing agents, and Part C looks at manganese's colorful states, each part specifying steps for chemical additions and observation recordings.
- 8.2: Redox Reactions - Pre-lab
- This page details a laboratory exercise on the oxidation states of iron ions, highlighting the use of potassium thiocyanate to confirm the oxidation of iron(II) to iron(III) and identifying relevant oxidizing agents. It also describes the role of potassium ferricyanide in reducing iron(III) back to iron(II) and examines the oxidation of the sulfite ion to sulfate, guiding students in assigning oxidation numbers to sulfur in both states.
- 8.3: Redox Reactions - Data and Report
- This page details a laboratory experiment investigating the reactions of iron and manganese with oxidizing and reducing agents. It provides data tables for recording color changes and includes post-lab questions on oxidation numbers, half-reactions, and balanced equations.