Textbook Question
Classify each of the following unbalanced half-reactions as either an oxidation or a reduction. (c) MnO4-(aq) → MnO42-(aq)
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Ch.19 - Electrochemistry
McMurry8th EditionChemistryISBN: 9781292336145
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Table of contents
- Ch.1 - Chemical Tools: Experimentation & Measurement143
- Ch.2 - Atoms, Molecules & Ions134
- Ch.3 - Mass Relationships in Chemical Reactions149
- Ch.4 - Reactions in Aqueous Solution157
- Ch.5 - Periodicity & Electronic Structure of Atoms92
- Ch.6 - Ionic Compounds: Periodic Trends and Bonding Theory73
- Ch.7 - Covalent Bonding and Electron-Dot Structures47
- Ch.8 - Covalent Compounds: Bonding Theories and Molecular Structure51
- Ch.9 - Thermochemistry: Chemical Energy104
- Ch.10 - Gases: Their Properties & Behavior138
- Ch.11 - Liquids & Phase Changes43
- Ch.12 - Solids and Solid-State Materials56
- Ch.13 - Solutions & Their Properties98
- Ch.14 - Chemical Kinetics79
- Ch.15 - Chemical Equilibrium107
- Ch.16 - Aqueous Equilibria: Acids & Bases94
- Ch.17 - Applications of Aqueous Equilibria125
- Ch.18 - Thermodynamics: Entropy, Free Energy & Equilibrium66
- Ch.19 - Electrochemistry130
- Ch.20 - Nuclear Chemistry73
- Ch.21 - Transition Elements and Coordination Chemistry122
- Ch.22 - The Main Group Elements155
- Ch.23 - Organic and Biological Chemistry43
Chapter 19, Problem 42b
Classify each of the following unbalanced half-reactions as either an oxidation or a reduction. (b) Pt2+ (aq) → Pt(s)
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Identify the oxidation states of platinum in both the reactant and the product. In the reactant, Pt has an oxidation state of +2, and in the product, Pt is in its elemental form, which has an oxidation state of 0.
Compare the oxidation states of platinum in the reactant and the product. The oxidation state decreases from +2 in the reactant to 0 in the product.
Recall the definition of reduction and oxidation in terms of oxidation states. Reduction involves a decrease in oxidation state, while oxidation involves an increase.
Apply the definitions to the reaction. Since the oxidation state of platinum decreases, this indicates a gain of electrons.
Conclude that the half-reaction Pt2+ (aq) → Pt(s) is a reduction process because it involves a decrease in oxidation state, indicating a gain of electrons.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Oxidation and Reduction
Oxidation and reduction are chemical processes that involve the transfer of electrons between species. Oxidation refers to the loss of electrons, resulting in an increase in oxidation state, while reduction involves the gain of electrons, leading to a decrease in oxidation state. These processes are always coupled, meaning that when one species is oxidized, another must be reduced.
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Oxidation and Reduction Reactions
Half-Reactions
Half-reactions are equations that show either the oxidation or reduction process separately. They are useful for balancing redox reactions and understanding the electron transfer involved. Each half-reaction includes the species undergoing oxidation or reduction, along with the electrons gained or lost, allowing for a clearer analysis of the overall reaction.
Identifying Oxidation States
Identifying oxidation states is crucial for determining whether a half-reaction is an oxidation or reduction. The oxidation state of an element in a compound indicates its degree of oxidation. In the given half-reaction, Pt<sup>2+</sup> has a +2 oxidation state, while solid Pt has an oxidation state of 0, indicating that Pt<sup>2+</sup> is being reduced to Pt(s) by gaining electrons.
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Related Practice
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Sketch a cell with inert electrodes suitable for electrolysis of aqueous CuBr2. (b) Indicate the direction of electron and ion flow.
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Classify each of the following unbalanced half-reactions as either an oxidation or a reduction. (d) CH3O→H(aq) CH2O(aq)
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Classify each of the following unbalanced half-reactions as either an oxidation or a reduction. (b) H2O2(aq) → O2(g)
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Textbook Question
Porous pellets of TiO2 can be reduced to titanium metal at the cathode of an electrochemical cell containing molten CaCl2 as the electrolyte. When the TiO2 is reduced, the O2-ions dis-solve in the CaCl2 and are subsequently oxidized to O2 gas at the anode. This approach may be the basis for a less expensive process than the one currently used for producing titanium.
(c) Write balanced equations for the anode, cathode, and overall cell reactions.
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Textbook Question
Consider a Daniell cell with 1.0 M ion concentrations: Does the cell voltage increase, decrease, or remain the same when each of the following changes is made? Explain. (a) Write a balanced equation for each cell reaction.
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