Book cover for Chemistry and Chemical Reactivity

Chemistry and Chemical Reactivity

John C. Kotz, Paul M. Treichel, John R. Townsend

ISBN #9780840048288

8th Edition

2,165 Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This section reviews the fundamental acid–base concepts, including both the Brønsted–Lowry and Lewis definitions. It covers how to write balanced acid–base reactions, use ICE tables for analyzing equilibrium and calculating pH, and understand how molecular structure, such as bond strength and resonance stabilization, influences acid strength. Special topics such as polyprotic acids, leveling effects in water, and the behavior of acids and bases in nonaqueous solvents (leading to superacids) are also discussed. Overall, mastering these concepts enables prediction of reaction outcomes and quantitative pH analyses in various chemical systems.

Learning Objectives

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Key Concepts

CONCEPT

DEFINITION

Brønsted–Lowry and Lewis definitions

A study of acid–base concepts encompassing both the Brønsted–Lowry and Lewis definitions. This topic explains how to write balanced acid–base reactions, analyze equilibria using ICE tables, and understand molecular influences (such as bond strength and resonance) on acid strength.

Example Problems

Example 1

Write the formula and give the name of the conjugate base of each of the following acids. (a) HCN (b) $\mathrm{HSO}_{4}^{-}$ (c) HF

Example 2

Write the formula and give the name of the conjugate acid of each of the following bases. (a) $\mathrm{NH}_{3}$ (b) $\mathrm{HCO}_{3}^{-}$ (c) $\mathrm{Br}^{-}$

Example 3

What are the products of each of the following acid-base reactions? Indicate the acid and its conjugate base and the base and its conjugate acid. (a) $\mathrm{HNO}_{3}+\mathrm{H}_{2} \mathrm{O} \rightarrow$ (b) $\mathrm{HSO}_{4}^{-}+\mathrm{H}_{2} \mathrm{O} \rightarrow$ (c) $\mathrm{H}_{3} \mathrm{O}^{+}+\mathrm{F}^{-} \rightarrow$

Example 4

What are the products of each of the following acid-base reactions? Indicate the acid and its conjugate base and the base and its conjugate acid. (a) $\mathrm{HClO}_{4}+\mathrm{H}_{2} \mathrm{O} \rightarrow$ (b) $\mathrm{NH}_{4}^{+}+\mathrm{H}_{2} \mathrm{O} \rightarrow$ (c) $\mathrm{HCO}_{3}^{-}+\mathrm{OH}^{-} \rightarrow$

Example 5

Write balanced equations showing how the hydrogen oxalate ion, $\mathrm{HC}_{2} \mathrm{O}_{4}^{-},$ can be both a Bronsted acid and a Bronsted base.
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Step-by-Step Explanations

QUESTION

How do you determine the acid dissociation constant (Ka) for a weak acid using its measured pH?\nStep-by-step Answer:\nStep 1: Write the ionization equation for the acid, HA + H2O \u21cc H3O+ + A\u2013.\nStep 2: Set up an ICE table with Initial, Change, and Equilibrium concentrations. Let the initial concentration of HA be given and assume initial [H3O+] and [A\u2013] are zero.\nStep 3: Convert the measured pH to [H3O+] using the equation [H3O+] = 10^(\u2013pH), and assign this value as the change x.\nStep 4: Write the equilibrium concentrations: [HA] = initial concentration \u2013 x, [H3O+] = x, and [A\u2013] = x.\nStep 5: Substitute these values into the equilibrium expression Ka = ([H3O+][A\u2013])/[HA] and solve for Ka.\nFinal Answer: Ka is obtained as (x^2)/(initial concentration \u2013 x), using the measured pH to find x.\n\n- Topic: Predicting Reaction Direction in Acid\u2013Base Equilibria \nQuestion: How can you predict whether an acid\u2013base reaction will lie to the right or left at equilibrium?\nStep-by-step Answer:\nStep 1: Identify the acid and base on the reactant side and determine their conjugate counterparts.\nStep 2: Compare the strengths using Ka for acids and Kb for bases; the reaction generally proceeds from a stronger acid and stronger base to form a weaker acid and weaker base.\nStep 3: Use the equilibrium constant relationship (Ka \u00d7 Kb = Kw) for conjugate pairs to help predict which side is favored.\nStep 4: Conclude that the reaction will favor the formation of the weaker acid and base if the equilibrium constant calculated is large.\nFinal Answer: The reaction proceeds if the reactants are stronger (in acid/base terms) than the products, driving equilibrium to the right.\n\n"

STEP-BY-STEP ANSWER:

Step 1: Write the ionization equation for the acid, HA + H2O \u21cc H3O+ + A\u2013.\nStep 2: Set up an ICE table with Initial, Change, and Equilibrium concentrations. Let the initial concentration of HA be given and assume initial [H3O+] and [A\u2013] are zero.\nStep 3: Convert the measured pH to [H3O+] using the equation [H3O+] = 10^(\u2013pH), and assign this value as the change x.\nStep 4: Write the equilibrium concentrations: [HA] = initial concentration \u2013 x, [H3O+] = x, and [A\u2013] = x.\nStep 5: Substitute these values into the equilibrium expression Ka = ([H3O+][A\u2013])/[HA] and solve for Ka.\nFinal Answer: Ka is obtained as (x^2)/(initial concentration \u2013 x), using the measured pH to find x.\n\n- Topic: Predicting Reaction Direction in Acid\u2013Base Equilibria \nQuestion: How can you predict whether an acid\u2013base reaction will lie to the right or left at equilibrium?\nStep-by-step Answer:\nStep 1: Identify the acid and base on the reactant side and determine their conjugate counterparts.\nStep 2: Compare the strengths using Ka for acids and Kb for bases; the reaction generally proceeds from a stronger acid and stronger base to form a weaker acid and weaker base.\nStep 3: Use the equilibrium constant relationship (Ka \u00d7 Kb = Kw) for conjugate pairs to help predict which side is favored.\nStep 4: Conclude that the reaction will favor the formation of the weaker acid and base if the equilibrium constant calculated is large.\nFinal Answer: The reaction proceeds if the reactants are stronger (in acid/base terms) than the products, driving equilibrium to the right.\n\n"
Final Answer: Ka is obtained as (x^2)/(initial concentration \u2013 x), using the measured pH to find x.\n\n- Topic: Predicting Reaction Direction in Acid\u2013Base Equilibria \nQuestion: How can you predict whether an acid\u2013base reaction will lie to the right or left at equilibrium?\nStep-by-step Answer:\nStep 1: Identify the acid and base on the reactant side and determine their conjugate counterparts.\nStep 2: Compare the strengths using Ka for acids and Kb for bases; the reaction generally proceeds from a stronger acid and stronger base to form a weaker acid and weaker base.\nStep 3: Use the equilibrium constant relationship (Ka \u00d7 Kb = Kw) for conjugate pairs to help predict which side is favored.\nStep 4: Conclude that the reaction will favor the formation of the weaker acid and base if the equilibrium constant calculated is large.\nFinal Answer: The reaction proceeds if the reactants are stronger (in acid/base terms) than the products, driving equilibrium to the right.\n\n"

"- Topic: Calculating Ka from pH using ICE Table \nQuestion: How do you determine the acid dissociation constant (Ka) for a weak acid using its measured pH?\nStep-by-step Answer:\nStep 1: Write the ionization equation for the acid, HA + H2O \u21cc H3O+ + A\u2013.\nStep 2: Set up an ICE table with Initial, Change, and Equilibrium concentrations. Let the initial concentration of HA be given and assume initial [H3O+] and [A\u2013] are zero.\nStep 3: Convert the measured pH to [H3O+] using the equation [H3O+] = 10^(\u2013pH), and assign this value as the change x.\nStep 4: Write the equilibrium concentrations: [HA] = initial concentration \u2013 x, [H3O+] = x, and [A\u2013] = x.\nStep 5: Substitute these values into the equilibrium expression Ka = ([H3O+][A\u2013])/[HA] and solve for Ka.\nFinal Answer: Ka is obtained as (x^2)/(initial concentration \u2013 x), using the measured pH to find x.\n\n- Topic: Predicting Reaction Direction in Acid\u2013Base Equilibria \nQuestion: How can you predict whether an acid\u2013base reaction will lie to the right or left at equilibrium?\nStep-by-step Answer:\nStep 1: Identify the acid and base on the reactant side and determine their conjugate counterparts.\nStep 2: Compare the strengths using Ka for acids and Kb for bases; the reaction generally proceeds from a stronger acid and stronger base to form a weaker acid and weaker base.\nStep 3: Use the equilibrium constant relationship (Ka \u00d7 Kb = Kw) for conjugate pairs to help predict which side is favored.\nStep 4: Conclude that the reaction will favor the formation of the weaker acid and base if the equilibrium constant calculated is large.\nFinal Answer: The reaction proceeds if the reactants are stronger (in acid/base terms) than the products, driving equilibrium to the right.\n\n"

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