Complete and balance the following half-reactions in basic solution. In each case, indicate whether the half-reaction is an oxidation or a reduction.


a. OH−(𝑎𝑞)⟶O2(𝑔)
b. SO32−(𝑎𝑞)⟶SO42−(𝑎𝑞)
c. N2(𝑔)⟶NH3(𝑔)
d. HO2−(𝑎𝑞)⟶OH−(𝑎𝑞)

Verified step by step guidance

1. Step 1: Identify the oxidation states of the elements in each half-reaction to determine whether it is an oxidation or reduction process.
2. Step 2: For each half-reaction, balance the atoms other than oxygen and hydrogen first.
3. Step 3: Balance the oxygen atoms by adding H2O molecules to the side that needs oxygen.
4. Step 4: Balance the hydrogen atoms by adding H+ ions to the side that needs hydrogen.
5. Step 5: Since the reactions are in basic solution, add OH− ions to both sides of the equation to neutralize the H+ ions, forming water, and then simplify the equation if necessary.

Key Concepts

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. Understanding these concepts is crucial for identifying the nature of half-reactions in redox processes.

Balancing Redox Reactions

Balancing redox reactions, especially in basic solutions, requires the use of half-reaction methods. This involves separating the oxidation and reduction processes, balancing the atoms and charges, and then combining the half-reactions. In basic solutions, hydroxide ions (OH−) are often added to neutralize any hydrogen ions (H+) that may appear during the balancing process.

Basic Solution Conditions

In a basic solution, the presence of hydroxide ions (OH−) influences the behavior of the chemical species involved in the reaction. This affects how half-reactions are balanced, as additional steps may be required to account for the basic environment. Recognizing the conditions of the solution is essential for correctly completing and balancing the half-reactions presented in the question.