Book cover for Chemistry The Science in Context

Chemistry The Science in Context

Thomas R. Gilbert

ISBN #9780393615142

5th Edition

2,675 Questions

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191,124 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This chapter explores the dynamics of chemical reactions in aqueous solutions, emphasizing the calculation and expression of solution concentrations, the formulation of balanced equations in different formats, and the analysis of various reaction types including acid–base, precipitation, and redox reactions. Key real-world applications, such as water softening through ion exchange, underscore the relevance of these chemical principles in environmental and biological systems.

Learning Objectives

1

Explain the fundamental principles governing chemical reactions in aqueous solutions.

2

Calculate solution concentrations using stoichiometry and titration data.

3

Write balanced chemical equations in molecular, ionic, and net ionic forms.

4

Analyze various reaction types including acid–base (Brønsted–Lowry), precipitation, and oxidation–reduction processes.

5

Apply concepts such as ion exchange in real-world contexts like water softening.

Key Concepts

CONCEPT

DEFINITION

Aqueous Solution

A solution in which water is the solvent and in which chemical species react.

Stoichiometry

The quantitative relationship between reactants and products in a chemical reaction.

Titration

An experimental method used to determine the concentration of a solute in a solution by reacting it with a standard solution.

Brønsted–Lowry Acid–Base Theory

A theory that defines acids as proton donors and bases as proton acceptors.

Precipitation Reaction

A chemical reaction in which soluble ions combine to form an insoluble compound (precipitate) guided by solubility rules.

Redox Reaction

A reaction involving the transfer of electrons between chemical species, where one species is oxidized and the other is reduced.

Ion Exchange

A process where ions are exchanged between a solution and an ion exchange material, commonly used in water softening.

Activity Series

A ranking of elements, especially metals, based on their reactivity, which helps predict the course of redox reactions.

Example Problems

Example 1

In Figure P4.1, which shows a solution containing three binary acids, one of the three is a weak acid and the other two are strong acids. Which color sphere represents the anion of the dissociated weak acid?

Example 2

Solutions of sodium chloride and silver iodide are mixed together and vigorously shaken. Which colored spheres in Figure P4.2 represent the following ions? (a) $\mathrm{Na}^{+}$ (b) $\mathrm{Cl}^{-} ;$ (c) $\mathrm{I}^{-}$

Example 3

Which of the highlighted elements in Figure P4.3 forms an acid with the following generic formula? (a) HX; (b) $\mathrm{H}_{2} \mathrm{XO}_{4} ;$ (c) $\mathrm{HXO}_{3} ;$ (d) $\mathrm{H}_{3} \mathrm{XO}_{4}$

Example 4

In which of the highlighted groups of elements in Figure P4.4 will you find an element that forms the following? (a) insoluble halides; (b) insoluble hydroxides; (c) hydroxides that are soluble; (d) binary compounds with hydrogen that are strong acids

Example 5

Which of the drawings in Figure P4.5 depicts a strong electrolyte? A weak electrolyte? A strong acid? A weak acid? A nonelectrolyte? Each drawing may fit more than one category.

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Step-by-Step Explanations

QUESTION

How do you calculate the concentration of an acid solution using titration data?

STEP-BY-STEP ANSWER:

Step 1: Write the balanced chemical equation for the titration reaction between the acid and the base.
Step 2: Calculate the number of moles of titrant used based on its concentration and the volume dispensed.
Step 3: Use the stoichiometric ratio from the balanced equation to determine the number of moles of the acid present in the sample.
Step 4: Calculate the molarity of the acid solution by dividing the moles of acid by the volume of the acid solution in liters.
Final Answer: The molarity of the acid is determined after converting the moles of acid appropriately using the titration data and stoichiometric relationship.

Titration Calculation

QUESTION

How do you balance a redox reaction in an aqueous solution?

STEP-BY-STEP ANSWER:

Step 1: Separate the overall reaction into oxidation and reduction half-reactions.
Step 2: Balance all atoms in each half-reaction except hydrogen and oxygen.
Step 3: Balance oxygen atoms by adding water (H2O) molecules and hydrogen atoms by adding hydrogen ions (H+), if in an acidic solution (or OH− in a basic solution).
Step 4: Balance the charges by adding electrons (e−) to the more positive side of each half-reaction.
Step 5: Multiply the half-reactions by appropriate factors so that the electrons cancel when the half-reactions are added together.
Step 6: Combine the half-reactions to obtain the balanced overall redox equation.
Final Answer: A balanced redox equation where both mass and charge are conserved.

Balancing a Redox Reaction

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Common Mistakes

  • Confusing molecular equations with net ionic equations, leading to incomplete representations of chemical reactions.
  • Misapplying stoichiometric ratios during titration calculations, resulting in incorrect concentration values.
  • Neglecting the proper balancing of redox half-reactions, especially overlooking the balance of charge by electrons.
  • Overlooking solubility rules when predicting precipitation reactions, which can lead to inaccurate predictions of product formation.
  • Assuming that all aqueous reactions involve complete dissociation, ignoring the behavior of nonelectrolytes.