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Ch.20 - Electrochemistry
Chapter 20, Problem 30

Complete and balance the following equations, and identify the oxidizing and reducing agents. (Recall that the O atoms in hydrogen peroxide, H2O2, have an atypical oxidation state.)


a. S(s) + HNO3(aq) → H2SO3(aq) + N2O(g) (acidic solution)
b. BrO3-(aq) + N2H4(g) → Br-(aq) + N2(g) (acidic solution)
c. H2O2(aq) + ClO2(aq) → ClO20(aq) _ O2(g) (basic solution)

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1
Identify the oxidation states of all elements in the reactants and products for each equation. This will help determine which elements are oxidized and reduced.
For each equation, write the half-reactions for the oxidation and reduction processes. Remember that oxidation involves an increase in oxidation state, while reduction involves a decrease.
Balance each half-reaction separately. In acidic solutions, add H+ ions and water molecules as needed to balance hydrogen and oxygen atoms. In basic solutions, use OH- ions and water.
Combine the balanced half-reactions, ensuring that the electrons lost in the oxidation half-reaction equal the electrons gained in the reduction half-reaction.
Identify the oxidizing and reducing agents. The oxidizing agent is the species that is reduced, and the reducing agent is the species that is oxidized.>

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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 substances. 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. In redox reactions, one species is oxidized and another is reduced, making it essential to identify these changes to balance the equations correctly.
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Balancing Redox Reactions

Balancing redox reactions requires ensuring that both mass and charge are conserved. This often involves separating the reaction into half-reactions for oxidation and reduction, balancing each half for atoms and charge, and then combining them. In acidic or basic solutions, additional steps may include adding H+ ions or OH- ions to balance hydrogen and oxygen atoms, respectively.
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Identifying Oxidizing and Reducing Agents

In a redox reaction, the oxidizing agent is the substance that gains electrons and is reduced, while the reducing agent is the substance that loses electrons and is oxidized. Identifying these agents is crucial for understanding the reaction's dynamics and predicting the products. This can be determined by analyzing the changes in oxidation states of the elements involved in the reaction.
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