chapter 15 acid–base equilibria. chapter 15 table of contents copyright © cengage learning. all...
TRANSCRIPT
![Page 1: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/1.jpg)
Chapter 15
Acid–Base Equilibria
![Page 2: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/2.jpg)
Chapter 15
Table of Contents
Copyright © Cengage Learning. All rights reserved 2
15.1Solutions of Acids or Bases Containing a Common Ion
15.2 Buffered Solutions
15.3 Buffering Capacity
15.4 Titrations and pH Curves
15.5 Acid–Base Indicators
![Page 3: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/3.jpg)
Section 15.1
Solutions of Acids or Bases Containing a Common Ion
Return to TOC
Copyright © Cengage Learning. All rights reserved 3
Common Ion Effect
• Shift in equilibrium position that occurs because of the addition of an ion already involved in the equilibrium reaction.
• An application of Le Châtelier’s principle.
![Page 4: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/4.jpg)
Section 15.1
Solutions of Acids or Bases Containing a Common Ion
Return to TOC
Copyright © Cengage Learning. All rights reserved 4
Example
HCN(aq) + H2O(l) H3O+(aq) + CN-
(aq)
• Addition of NaCN will shift the equilibrium to the left because of the addition of CN-, which is already involved in the equilibrium reaction.
• A solution of HCN and NaCN is less acidic than a solution of HCN alone.
![Page 5: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/5.jpg)
Section 15.2
Atomic MassesBuffered Solutions
Return to TOC
Copyright © Cengage Learning. All rights reserved 5
Key Points about Buffered Solutions
• Buffered Solution – resists a change in pH.• They are weak acids or bases containing a
common ion.• After addition of strong acid or base, deal with
stoichiometry first, then the equilibrium.
![Page 6: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/6.jpg)
Section 15.2
Atomic MassesBuffered Solutions
Return to TOC
Copyright © Cengage Learning. All rights reserved 6
Henderson–Hasselbalch Equation
a
ApH = p + log
HA
K
• For a particular buffering system (conjugate acid–base pair), all solutions that have the same ratio [A–] / [HA] will have the same pH.
![Page 7: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/7.jpg)
Section 15.2
Atomic MassesBuffered Solutions
Return to TOC
Copyright © Cengage Learning. All rights reserved 7
Exercise
What is the pH of a buffer solution that is 0.45 M acetic acid (HC2H3O2) and 0.85 M sodium acetate (NaC2H3O2)? The Ka for acetic acid is 1.8 × 10–5.
pH = 5.02
![Page 8: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/8.jpg)
Section 15.2
Atomic MassesBuffered Solutions
Return to TOC
Copyright © Cengage Learning. All rights reserved 8
![Page 9: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/9.jpg)
Section 15.3
The Mole Buffering Capacity
Return to TOC
Copyright © Cengage Learning. All rights reserved 9
• The amount of protons or hydroxide ions the buffer can absorb without a significant change in pH.
• Determined by the magnitudes of [HA] and [A–].• A buffer with large capacity contains large
concentrations of the buffering components.
![Page 10: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/10.jpg)
Section 15.3
The Mole Buffering Capacity
Return to TOC
The amount of H+ or OH- that buffered solution can absorb without a significant change in pH
Buffer capacity measures how well a solution resists changes in pH when acid or base is added. The greater the buffer capacity, the less the pH changes.
![Page 11: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/11.jpg)
Section 15.3
The Mole Buffering Capacity
Return to TOC
0.67
0.06
0.04
HA
A1
0.05
0.05
HA
A
:B
0.9965.01
4.99
HA
A1
5.00
5.00
HA
A
:A
H mol 0.01
H mol 0.01
2) Magnitudes of [HA] and [A-] the capacity of a buffered soln.
Ex : soln A : 5.00 M HOAc + 5.00 M NaOAc soln B : 0.05 M HOAc + 0.05 M NaOAc pH change when 0.01 mol of HCl(g) is added
![Page 12: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/12.jpg)
Section 15.3
The Mole Buffering Capacity
Return to TOC
3) [A-] / [HA] ratio the pH of a buffered soln.
soln new 50.5% soln original
49.5HA
A100
0.01
1.00
HA
A
0.98HA
A1.00
1.00
1.00
HA
A
2% :C
H mol 0.01
H mol 0.01
![Page 13: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/13.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 13
The pH Curve for the Titration of 50.0 mL of 0.200 M HNO3 with 0.100 M NaOH
![Page 14: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/14.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 14
The pH Curve for the Titration of 100.0 mL of 0.50 M NaOH with 1.0 M HCI
![Page 15: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/15.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 15
Concept Check
Consider a solution made by mixing 0.10 mol of HCN (Ka = 6.2 x 10–10) with 0.040 mol NaOH in 1.0 L of aqueous solution.
What are the major species immediately upon mixing (that is, before a reaction)?
HCN, Na+, OH–, H2O
![Page 16: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/16.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 16
Let’s Think About It…
K = 1.8 x 109
HC2H3O2(aq) + OH– C2H3O2–(aq) + H2O
Before 0.20 mol 0.030 mol 0
Change –0.030 mol –0.030 mol +0.030 mol
After 0.17 mol 0 0.030 mol
![Page 17: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/17.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 17
Steps Toward Solving for pH
Ka = 1.8 x 10–5
pH = 3.99
HC2H3O2(aq) + H2O H3O+ + C2H3O2-(aq)
Initial 0.170 M ~0 0.030 M
Change –x +x +x
Equilibrium 0.170 – x x 0.030 + x
![Page 18: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/18.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 18
Exercise
Calculate the pH of a 100.0 mL solution of 0.100 M acetic acid (HC2H3O2), which has a Ka value of 1.8 x 10–5.
pH = 2.87
![Page 19: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/19.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 19
Concept Check
Calculate the pH of a solution made by mixing 100.0 mL of a 0.100 M solution of acetic acid (HC2H3O2), which has a Ka value of 1.8 x 10–5, and 50.0 mL of a 0.10 M NaOH solution.
pH = 4.74
![Page 20: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/20.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 20
Concept Check
Calculate the pH of a solution at the equivalence point when 100.0 mL of a 0.100 M solution of acetic acid (HC2H3O2), which has a Ka value of 1.8 x 10–5, is titrated with a 0.10 M NaOH solution.
pH = 8.72
![Page 21: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/21.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 21
The pH Curve for the Titration of 50.0 mL of 0.100 M HC2H3O2 with 0.100 M NaOH
![Page 22: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/22.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 22
The pH Curves for the Titrations of 50.0-mL Samples of 0.10 M Acids with Various Ka Values with 0.10 M NaOH
![Page 23: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/23.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Copyright © Cengage Learning. All rights reserved 23
The pH Curve for the Titration of 100.0mL of 0.050 M NH3 with 0.10 M HCl
![Page 24: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/24.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
P.228
Kjeldahl Nitrogen Analysis :
developed in 1883, the analysis remains one of the most widely used methods for determining nitrogen in organic substances such as protein, cereal, and flour.
![Page 25: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/25.jpg)
Section 15.4
Titrations and pH Curves
Return to TOC
Melamine contaminated milk
![Page 26: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/26.jpg)
Section 15.5
Acid–Base Indicators
Return to TOC
Copyright © Cengage Learning. All rights reserved 26
• Marks the end point of a titration by changing color.
• The equivalence point is not necessarily the same as the end point (but they are ideally as close as possible).
![Page 27: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/27.jpg)
Section 15.5
Acid–Base Indicators
Return to TOC
Copyright © Cengage Learning. All rights reserved 27
The Acid and Base Forms of the Indicator Phenolphthalein
![Page 28: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/28.jpg)
Section 15.5
Acid–Base Indicators
Return to TOC
Copyright © Cengage Learning. All rights reserved 28
The Methyl Orange Indicator is Yellow in Basic Solution and Red in Acidic Solution
![Page 29: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/29.jpg)
Section 15.5
Acid–Base Indicators
Return to TOC
1) Usually a weak organic acid or base that has distinctly different colors in its nonionized & ionized forms.
HIn(aq) H+(aq) + In-
(aq) pKHIn
nonionized ionized
form form
![Page 30: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/30.jpg)
Section 15.5
Acid–Base Indicators
Return to TOC
1)
2)
3)
-
HIn
-
HIn
In & HIn of color the of ncombinatio
InHIn
1pKpH
In of color theshow 10
HIn
In
1-pKpH
HIn of color theshow 10
In
HIn
![Page 31: Chapter 15 Acid–Base Equilibria. Chapter 15 Table of Contents Copyright © Cengage Learning. All rights reserved 2 15.1Solutions of Acids or Bases Containing](https://reader035.vdocuments.us/reader035/viewer/2022062511/551c2527550346ad4f8b5d4d/html5/thumbnails/31.jpg)
Section 15.5
Acid–Base Indicators
Return to TOC
Copyright © Cengage Learning. All rights reserved 31
Useful pH Ranges for Several Common Indicators