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

Molecular Equations

GOB Chemistry

5. Classification & Balancing of Chemical Reactions

Molecular Equations

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3:51 minutes

Problem 20

Textbook Question

An aqueous solution of a cation (represented as blue spheres in the diagram) is allowed to mix with a solution of an anion (represented as green spheres) and the following result is obtained:

Which combinations of cation and anion, chosen from the following lists, are compatible with the observed results? Explain.
Cations: Na⁺, Ca²⁺, Ag⁺, Ni²⁺
Anions: Cl⁻, CO₂^3–, CrO₄^2–, NO₃^–

Verified step by step guidance

Step 1: Analyze the image provided. The diagram shows two solutions being mixed: one containing green spheres (representing anions) and the other containing red spheres (representing cations). After mixing, a solid precipitate forms at the bottom of the container, indicating that a chemical reaction has occurred and a precipitate has formed.

Step 2: Understand the concept of solubility rules. Precipitation occurs when the product of a reaction between a cation and an anion is insoluble in water. Use solubility rules to determine which combinations of cations and anions can form an insoluble compound.

Step 3: Evaluate the possible combinations of cations and anions provided in the problem. The cations are Na+, Ca2+, Ag+, and Ni2+, and the anions are Cl−, CO3^2−, CrO4^2−, and NO3−. Cross-reference these ions with solubility rules to identify which combinations produce an insoluble compound.

Step 4: Apply solubility rules to each combination. For example, Ag+ often forms insoluble compounds with Cl− (AgCl is insoluble), while Na+ typically forms soluble compounds with all the anions listed. Similarly, Ca2+ can form insoluble compounds with CO3^2− (CaCO3 is insoluble). Continue this process for all combinations.

Step 5: Based on the solubility rules and the observed precipitation in the diagram, identify the specific cation and anion pair that is compatible with the results. Ensure the pair corresponds to an insoluble compound forming a precipitate, as shown in the image.

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Key Concepts

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

Ionic Compounds

Ionic compounds are formed when cations (positively charged ions) and anions (negatively charged ions) combine due to electrostatic forces. The stability of these compounds depends on the charge and size of the ions involved. In the context of the question, understanding how different cations and anions interact is crucial for predicting which combinations will form stable ionic compounds.

Solubility Rules

Solubility rules are guidelines that help predict whether an ionic compound will dissolve in water. Certain combinations of cations and anions are known to be soluble or insoluble based on these rules. For example, compounds containing Na+ or NO3− are generally soluble, while others may form precipitates. This concept is essential for determining the compatibility of the given cations and anions.

Precipitation Reactions

Precipitation reactions occur when two solutions containing soluble salts are mixed, resulting in the formation of an insoluble compound that precipitates out of solution. The image illustrates this process, showing layered spheres that suggest a solid formation. Identifying which combinations of cations and anions lead to precipitation is key to answering the question effectively.

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