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Ch.22 - Chemistry of the Nonmetals
Chapter 22, Problem 55

Complete the exercises below. Write complete balanced half-reactions for: a. oxidation of nitrous acid to nitrate ion in acidic solution, b. oxidation of N₂ to N₂O in acidic solution.

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Identify the species involved in the oxidation process for each reaction. For part (a), nitrous acid (HNO₂) is oxidized to nitrate ion (NO₃⁻). For part (b), nitrogen gas (N₂) is oxidized to nitrous oxide (N₂O).
Write the unbalanced half-reaction for each oxidation process. For part (a), start with HNO₂ → NO₃⁻. For part (b), start with N₂ → N₂O.
Balance the atoms other than oxygen and hydrogen in each half-reaction. For part (a), nitrogen is already balanced. For part (b), nitrogen is also balanced.
Balance the oxygen atoms by adding water (H₂O) molecules. For part (a), add H₂O to the right side to balance the oxygen atoms. For part (b), add H₂O to the right side to balance the oxygen atoms.
Balance the hydrogen atoms by adding hydrogen ions (H⁺) to the side that needs more hydrogen. For part (a), add H⁺ to the left side. For part (b), add H⁺ to the left side.

Key Concepts

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

Half-Reactions

Half-reactions are the individual oxidation or reduction processes that occur in a redox reaction. They show the transfer of electrons and the changes in oxidation states of the reactants. In a balanced half-reaction, the number of electrons lost in oxidation must equal the number of electrons gained in reduction, ensuring charge and mass balance.
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Oxidation States

Oxidation states (or oxidation numbers) indicate the degree of oxidation of an atom in a compound. They help in identifying which species is oxidized and which is reduced in a reaction. Understanding how to assign oxidation states is crucial for writing balanced half-reactions, as it allows one to track electron transfer and changes in chemical species.
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Oxidation Numbers

Acidic Solution Conditions

In an acidic solution, the presence of hydrogen ions (H⁺) influences the balance of half-reactions. Acidic conditions often require the addition of H⁺ ions and water molecules to balance the equation properly. Recognizing the role of H⁺ in the half-reaction process is essential for accurately representing the oxidation of species in acidic environments.
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