Book cover for Chemistry: An Atoms-Focused Approach

Chemistry: An Atoms-Focused Approach

Thomas R. Gilbert, Rein V. Kirss, Natalie Foster

ISBN #9780393284218

2nd Edition

2,756 Questions

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139,697 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

Thermochemistry involves studying how energy changes in chemical reactions and physical processes are measured and calculated. Key tools include calorimetry, Hess’s law, and the concepts of enthalpy, bond energy, and state functions. Using these principles, one can evaluate reaction energetics, compare fuels by their energy content, and even estimate lattice energies via Born–Haber cycles. Mastering these concepts is essential for both academic studies and practical applications in industry, environmental science, and everyday energy management.

Learning Objectives

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Key Concepts

CONCEPT

DEFINITION

Acid–Base Equilibria

The study of proton (H?) transfer processes between acids and bases, quantified by equilibrium constants (Ka, Kb, and Kw) and represented on a logarithmic pH scale. –

Example Problems

Example 1

Figure P9.1 shows the compression stroke of a diesel engine. How does upward motion of the piston alter the internal energy of the gases trapped in the cylinder? (FIGURE CAN'T COPY)

Example 2

Figure P9.2 shows the power stroke of a diesel engine as energy released by the rapid combustion of the air and fuel vapor inside the cylinder pushes the cylinder downward. If the gases inside the cylinder are a thermodynamic system, how does the internal energy of the system change as a result of the combustion reaction and downward motion of the piston? In your description indicate the signs on $\Delta E, q,$ and $w$. (FIGURE CAN'T COPY)

Example 3

Based on their molecular structures, predict which of the four hydrocarbons in Figure P9.3 has the highest fuel value and which has the lowest. (FIGURE CAN'T COPY)

Example 4

The diagram in Figure P9.4 shows how the volume of a reaction mixture at constant pressure and temperature changes as $\mathrm{N}_{2}$ and $\mathrm{H}_{2}$ combine, forming $\mathrm{NH}_{3}$. a. In this reaction, does the reaction mixture do work on the surroundings, or vice versa? b. Use data from Appendix 4 to calculate $\Delta H_{\text {rxn }}^{\circ}$ for the formation of one mole of product. c. To achieve a final temperature that is the same as the initial one, does heat flow out from, or into, the reaction mixture? (FIGURE CAN'T COPY)

Example 5

Assuming the reaction mixture in Figure P9.4 is a thermodynamic system, what are the signs on $q, w,$ and $\Delta E ?$ If each molecule in the figure represents one mole of reactant or product, what is the percent yield of the reaction?
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Step-by-Step Explanations

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Common Mistakes

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