Skip to main content
Pearson+ LogoPearson+ Logo
Ch.20 - Electrochemistry
All textbooksBrown 15th EditionCh.20 - ElectrochemistryProblem 25
Chapter 20, Problem 25

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. O2(𝑔)⟢H2O(𝑙)
b. Mn2+(π‘Žπ‘ž)⟢MnO2(𝑠)
c. Cr(OH)3(𝑠)⟢CrO42βˆ’(π‘Žπ‘ž)
d. N2H4(π‘Žπ‘ž)⟢N2(𝑔)

Verified step by step guidance
1
Step 1: Identify the oxidation states of the elements in the reactants and products to determine if the half-reaction is an oxidation or a reduction.
Step 2: For each half-reaction, balance the atoms other than oxygen and hydrogen first.
Step 3: Balance the oxygen atoms by adding H2O molecules to the side that needs oxygen.
Step 4: Balance the hydrogen atoms by adding H+ ions to the side that needs hydrogen.
Step 5: Since the solution is basic, add OH- ions to both sides of the equation to neutralize the H+ ions, forming water, and then simplify the equation by canceling out water molecules if possible.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4m
Was this helpful?

Key Concepts

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

Half-Reaction Method

The half-reaction method is a technique used to balance redox reactions by separating the oxidation and reduction processes. Each half-reaction shows the species being oxidized or reduced, along with the electrons involved. This method is particularly useful in basic solutions, where hydroxide ions (OH-) are added to balance the charges and atoms, ensuring that both mass and charge are conserved.
Recommended video:
Guided course
01:49
Method 1 of Radioactive Half-Life

Oxidation and Reduction

Oxidation refers to the loss of electrons from a substance, 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. Identifying which species undergoes these changes is crucial for balancing half-reactions and understanding the overall reaction mechanism.
Recommended video:
Guided course
01:53
Oxidation and Reduction Reactions

Basic Solution Conditions

In basic solutions, the presence of hydroxide ions (OH-) affects how half-reactions are balanced. When balancing in basic conditions, it is often necessary to add OH- ions to neutralize any H+ ions produced during the balancing process. This ensures that the final balanced equation accurately reflects the conditions of the reaction and maintains charge and mass balance.
Recommended video:
Guided course
01:04
Balancing Basic Redox Reactions
Related Practice
Textbook Question

Complete and balance the following half-reactions. In each case, indicate whether the half-reaction is an oxidation or a reduction. (a) Sn2+(aq) β†’ Sn4+(aq) (acidic solution) (b) TiO2(s) β†’ Ti2+(aq) (acidic solution) (c) ClO3-(aq) β†’ Cl-(aq) (acidic solution) (d) N2(g) β†’ NH4+(aq) (acidic solution)

Textbook Question

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. OHβˆ’(π‘Žπ‘ž)⟢O2(𝑔)

b. SO32βˆ’(π‘Žπ‘ž)⟢SO42βˆ’(π‘Žπ‘ž)

c. N2(𝑔)⟢NH3(𝑔)

d. HO2βˆ’(π‘Žπ‘ž)⟢OHβˆ’(π‘Žπ‘ž)

Textbook Question

Complete and balance the following half-reactions. In each case, indicate whether the half-reaction is an oxidation or a reduction. (f) SO32-1aq2 Β‘ SO42-1aq2 (basic solution)

1
views
Textbook Question

Complete and balance the following half-reactions in basic solution. In each case, indicate whether the half-reaction is an oxidation or a reduction. c. Cr(OH)3(𝑠)⟢CrO42βˆ’(π‘Žπ‘ž)

Textbook Question

Complete and balance the following half-reactions in acidic solution. In each case indicate whether the half-reaction is an oxidation or a reduction. b. H2SO3(π‘Žπ‘ž)⟢SO42βˆ’(π‘Žπ‘ž)

Textbook Question

Complete and balance the following equations, and identify the oxidizing and reducing agents: (a) Cr2O72-(aq) + I-(aq) β†’ Cr3+(aq) + IO3-(aq) (acidic solution) (b) MnO4-(aq) + CH3O(1aq) β†’ Mn2+(aq) + HCOOH(aq) (acidic solution) (c) I2(s) + OCl-(aq) β†’ IO3-(aq) + Cl-(aq) (acidic solution)