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Ch.19 - Electrochemistry
Chapter 19, Problem 41b

Balance each redox reaction occurring in basic aqueous solution. b. Al(s) + MnO4(aq) → MnO2(s) + Al(OH)4(aq)

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Identify the oxidation and reduction half-reactions. Al is oxidized to Al(OH)_4^- and MnO_4^- is reduced to MnO_2.
Write the oxidation half-reaction: Al(s) -> Al(OH)_4^-(aq). Balance Al atoms and then balance O by adding H2O and H by adding OH^-.
Write the reduction half-reaction: MnO_4^-(aq) -> MnO_2(s). Balance Mn atoms and then balance O by adding H2O and H by adding OH^-.
Balance the charge in each half-reaction by adding electrons. Ensure the number of electrons lost in the oxidation half-reaction equals the number gained in the reduction half-reaction.
Combine the balanced half-reactions, cancel out common species, and ensure mass and charge are balanced in the final equation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Redox Reactions

Redox reactions, or reduction-oxidation reactions, involve the transfer of electrons between two species. In these reactions, one species is oxidized (loses electrons) while the other is reduced (gains electrons). Understanding the oxidation states of the elements involved is crucial for identifying which species undergo oxidation and reduction.
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Balancing Redox Reactions in Basic Solution

When balancing redox reactions in basic solutions, hydroxide ions (OH-) are used to neutralize any hydrogen ions (H+) that may appear during the balancing process. This often involves adding OH- to both sides of the half-reactions to form water, which helps maintain the balance of charges and atoms in the overall reaction.
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Half-Reaction Method

The half-reaction method is a systematic approach to balancing redox reactions by separating the oxidation and reduction processes. Each half-reaction is balanced for mass and charge, and then the two balanced half-reactions are combined to form the overall balanced equation. This method is particularly useful in complex reactions, such as those occurring in basic solutions.
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