Table of contents

1. Matter and Measurements4h 31m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 27m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines39m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 41m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

5. Classification & Balancing of Chemical Reactions

Redox Reactions

GOB Chemistry

5. Classification & Balancing of Chemical Reactions

Redox Reactions

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1:23 minutes

Problem 45c

Textbook Question

Identify each of the following as an oxidation or a reduction:
c. Cr³⁺(aq) + 3e^– → Cr(s)

Verified step by step guidance

Step 1: Recall the definitions of oxidation and reduction. Oxidation is the loss of electrons, while reduction is the gain of electrons. A helpful mnemonic is 'OIL RIG' (Oxidation Is Loss, Reduction Is Gain).

Step 2: Analyze the given chemical equation: Cr³⁺(aq) + 3e⁻ → Cr(s). Notice that the chromium ion (Cr³⁺) is reacting with three electrons (3e⁻).

Step 3: Determine if electrons are being gained or lost. In this case, Cr³⁺ is gaining three electrons to form Cr(s).

Step 4: Conclude that the gain of electrons corresponds to a reduction process. Therefore, this reaction represents a reduction.

Step 5: Summarize the result: The reaction Cr³⁺(aq) + 3e⁻ → Cr(s) is a reduction because the chromium ion gains electrons to form a neutral chromium atom.

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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 species. Oxidation refers to the loss of electrons, while reduction refers to the gain of electrons. These processes are always coupled; when one species is oxidized, another must be reduced. Understanding these definitions is crucial for identifying the nature of chemical reactions.

Half-Reaction Method

The half-reaction method is a way to balance redox reactions by separating the oxidation and reduction processes. Each half-reaction shows either the loss or gain of electrons, making it easier to analyze the changes in oxidation states. This method is particularly useful in identifying which species is oxidized and which is reduced in a given reaction.

Oxidation States

Oxidation states (or numbers) indicate the degree of oxidation of an atom in a compound. They help in determining how many electrons are lost or gained during a reaction. In the given reaction, the oxidation state of chromium changes from +3 in Cr³⁺ to 0 in Cr(s), indicating that it is being reduced. Understanding oxidation states is essential for identifying the nature of the reaction.

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Related Practice

Multiple Choice

Which element is oxidized and which is reduced in the following reaction?

Hg (aq) + HgCl₂ (aq) → Hg₂Cl₂

Which of the following represents an oxidation-reduction reaction?

I. PCl₃ (aq) + Cl₂ (g) → PCl₅ (aq)

II. 2 AgNO₃ (aq) + Cu (s) → Cu(NO₃)₂ (aq) + 2 Ag (s)

III. CO₂ (g) + 2 LiOH (aq) → Li₂CO₃ (aq) + H₂O (l)

IV. FeCl₂ (aq) + 2 NaOH (aq) → Fe(OH)₂ (aq) + 2 NaCl (aq)

Identify the oxidized reactant, the reduced reactant, the oxidizing agent, and the reducing agent in the following reactions:

a. Fe(s) + Cu²⁺(aq) → Fe²⁺(aq) + Cu(s)

b. Mg(s) + Cl₂(g) → MgCl₂(s)

c. 2 Al(s) + Cr₂O₃(s) → 2 Cr(s) + Al₂O₃(s)

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Textbook Question

Potassium, a silvery metal, reacts with bromine, a corrosive, reddish liquid, to yield potassium bromide, a white solid. Write the balanced equation, and identify the oxidizing and reducing agents.

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Textbook Question

In the mitochondria of human cells, energy is provided by the oxidation and reduction reactions of the iron ions in the cytochromes in electron transport. Identify each of the following as an oxidation or a reduction:

a. Fe³⁺ + e^– → Fe²⁺

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Textbook Question

In each of the following, tell whether the substance gains electrons or loses electrons in a redox reaction:

a. An oxidizing agent

b. A reducing agent

c. A substance undergoing oxidation

d. A substance undergoing reduction

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Multiple Choice