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1. Module 8

1.25. Page 4

Lesson 5

Module 8—Acid-Base Equilibrium

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Equilibrium Constant for Bases, Kb

The analysis of the equilibrium of bases has many similarities to the analyses you have completed so far in this lesson. Read from “Calculating Kb from Amount Concentrations” on page 745 in the textbook to the start of “Calculating [OH–(aq)] from Kb” on page 746.

Self-Check

SC 5. Complete “Practice” questions 10–13 on page 746 in the textbook.

Check your work.

Self-Check Answers

Contact your teacher if your answers vary significantly from the answers provided here.

SC 5.

Practice 10.

Empirical Property	Expected Result with a Strong Base	Expected Result with a Weak Base
conductivity	strong electrolyte	weak electrolyte
pH	high	lower, but above 7
rate of reaction	higher	lower

Practice 11.

CN–(aq) + H2O(l) HCN(aq) + OH–(aq)
SO42–(aq) + H2O(l) HSO4– (aq) + OH–(aq)

Practice 12.

Amount Concentration	[C2H5COO–(aq)] (mol/L)	[C2H5COOH(aq)] (mol/L)	[OH–(aq)] (mol/L)
Initial	0.157	0	0
Change	–1.1 × 10–5	+1.1 × 10–5	+1.1 × 10–5
Equilibrium	0.157	1.1 × 10–5	1.1 × 10–5

Practice 13.

Amount Concentration	[C6H5NH2(aq)] (mol/L)	[C6H5NH3(aq)] (mol/L)	[OH–(aq)] (mol/L)
Initial	0.10	0	0
Change	–6.5 × 10–6	+6.5 × 10–6	+6.5 × 10–6
Equilibrium	0.10 (an insignificant change)	6.5 × 10–6	6.5 × 10–6

Read

A relationship exists between the three equilibrium constants you used in this module. Read pages 746–750 in the textbook, and work through the “Sample problems” and “Communication examples” in this section to learn more about the relationship between Ka, Kb, and Kw.