1. Additional Aspects of Aqueous Equilibria

2. Reaction of Weak Bases with Water
The base reacts with water, producing its conjugate acid and hydroxide ion:
CH3NH2 + H2O  CH3NH3+ + OH- Kb = 4.38 x 10-4

3. Kb for Some Common Weak Bases
Many students struggle with identifying weak bases and their conjugate acids.What patterns do you see that may help you?
Base
Formula
Conjugate Acid Kb
Ammonia 
 NH3
 NH4+
 1.8 x 10-5 
 Methylamine
 CH3NH2
 CH3NH3+
 4.38 x 10-4 
 Ethylamine
 C2H5NH2
 C2H5NH3+
 5.6 x 10-4 
 Diethylamine
 (C2H5)2NH
 (C2H5)2NH2+
 1.3 x 10-3 
 Triethylamine
  (C2H5)3N
  (C2H5)3NH+
 4.0 x 10-4 
 Hydroxylamine
 HONH2 
 HONH3+  
 1.1 x 10-8 
 Hydrazine
H2NNH2 
H2NNH3+  
 3.0 x 10-6 
 Aniline
 C6H5NH2 
 C6H5NH3+  
 3.8 x 10-10 
 Pyridine
 C5H5N 
 C5H5NH+  
 1.7 x 10-9 

4. Reaction of Weak Bases with Water
The generic reaction for a base reacting with water, producing its conjugate acid and hydroxide ion:
B + H2O  BH+ + OH-
(Yes, all weak bases do this – DO NOT
endeavor to make this complicated!)

5. Buffered Solutions
A solution that resists a change in pH when either hydroxide ions or protons are added.
Buffered solutions contain either:
A weak acid and its salt
A weak base and its salt

6. Acid/Salt Buffering Pairs
The salt will contain the anion of the acid, and the cation of a strong base (NaOH, KOH)
Weak Acid
Formula
of the acid
Example of a salt of the weak acid
 Hydrofluoric 
HF 
 KF – Potassium fluoride 
 Formic 
 HCOOH 
 KHCOO – Potassium formate 
 Benzoic 
 C6H5COOH 
 NaC6H5COO – Sodium benzoate
 Acetic 
 CH3COOH 
 NaH3COO – Sodium acetate 
 Carbonic 
 H2CO3 
 NaHCO3 - Sodium bicarbonate
 Propanoic 
 HC3H5O2 
  NaC3H5O2  - Sodium propanoate
 Hydrocyanic 
 HCN 
 KCN - potassium cyanide 

7. Base/Salt Buffering Pairs
The salt will contain the cation of the base, and the anion of a strong acid (HCl, HNO3)
Base
Formula of the base
Example of a salt of the weak acid
Ammonia 
 NH3
 NH4Cl - ammonium chloride
 Methylamine
 CH3NH2
 CH3NH2Cl – methylammonium chloride
 Ethylamine
 C2H5NH2
 C2H5NH3NO3 -  ethylammonium nitrate
 Aniline
 C6H5NH2 
C6H5NH3Cl – aniline hydrochloride
 Pyridine
 C5H5N 
  C5H5NHCl – pyridine hydrochloride

8. Titration of an Unbuffered Solution
A solution that is
0.10 M CH3COOH
is titrated with
0.10 M NaOH

9. Titration of a Buffered Solution
A solution that is
0.10 M CH3COOH and
0.10 M NaCH3COO is titrated with
0.10 M NaOH

10. Comparing Results
Buffered
Unbuffered

11. Comparing Results Unbuffered Buffered
In what ways are the graphs different?
In what ways are the graphs similar?

12. Henderson-Hasselbalch Equation

13. Weak Acid/Strong Base Titration
Endpoint is above pH 7
A solution that is
0.10 M CH3COOH
is titrated with
0.10 M NaOH

14. Strong Acid/Strong Base Titration
Endpoint is at
pH 7
A solution that is
0.10 M HCl is titrated with
0.10 M NaOH

15. Strong Acid/Strong Base Titration
A solution that is
0.10 M NaOH is titrated with
0.10 M HCl
Endpoint is at
pH 7
It is important to recognize that titration curves are not always increasing from left to right.

16. Strong Acid/Weak Base Titration
A solution that is
0.10 M HCl is titrated with
0.10 M NH3
Endpoint is below
pH 7

17. Selection of Indicators

18. Some Acid-Base Indicators
pH Range in which Color Change Occurs
Color Change as pH Increases
Crystal violet Thymol blue Orange IV Methyl orange Bromcresol green Methyl red Chlorophenol red Bromthymol blue Phenol red Neutral red Thymol blue Phenolphthalein Thymolphthalein Alizarin yellow Indigo carmine
yellow to blue red to yellow red to yellow red to yellow yellow to blue red to yellow yellow to red yellow to blue yellow to red red to amber yellow to blue colourless to pink colourless to blue yellow to blue blue to yellow

19. pH Indicators and their ranges

20. Ksp Values for Some Salts at 25C
Name
Formula
Ksp
 Barium carbonate 
 BaCO3 
 2.6 x 10-9 
 Barium chromate 
 BaCrO4 
 1.2 x 10-10 
 Barium sulfate 
 BaSO4 
 1.1 x 10-10 
 Calcium carbonate 
 CaCO3 
 5.0 x 10-9 
 Calcium oxalate 
 CaC2O4 
 2.3 x 10-9 
 Calcium sulfate 
 CaSO4 
 7.1 x 10-5 
 Copper(I) iodide 
 CuI 
 1.3 x 10-12 
 Copper(II) iodate 
 Cu(IO3)2 
 6.9 x 10-8 
 Copper(II) sulfide 
 CuS 
 6.0 x 10-37 
 Iron(II) hydroxide 
 Fe(OH)2 
 4.9 x 10-17 
 Iron(II) sulfide 
 FeS 
 6.0 x 10-19 
 Iron(III) hydroxide 
 Fe(OH)3 
 2.6 x 10-39 
 Lead(II) bromide 
 PbBr2 
 6.6 x 10-6 
 Lead(II) chloride 
 PbCl2 
 1.2 x 10-5 
 Lead(II) iodate 
 Pb(IO3)2 
 3.7 x 10-13 
 Lead(II) iodide 
 PbI2 
 8.5 x 10-9 
 Lead(II) sulfate 
 PbSO4 
 1.8 x 10-8 
Name
Formula
Ksp
 Lead(II) bromide 
 PbBr2 
 6.6 x 10-6 
 Lead(II) chloride 
 PbCl2 
 1.2 x 10-5 
 Lead(II) iodate 
 Pb(IO3)2 
 3.7 x 10-13 
 Lead(II) iodide 
 PbI2 
 8.5 x 10-9 
 Lead(II) sulfate 
 PbSO4 
 1.8 x 10-8 
 Magnesium carbonate 
 MgCO3 
 6.8 x 10-6 
 Magnesium hydroxide 
 Mg(OH)2 
 5.6 x 10-12 
 Silver bromate 
 AgBrO3 
 5.3 x 10-5 
 Silver bromide 
 AgBr 
 5.4 x 10-13 
 Silver carbonate 
 Ag2CO3 
 8.5 x 10-12 
 Silver chloride 
 AgCl 
 1.8 x 10-10 
 Silver chromate 
 Ag2CrO4 
 1.1 x 10-12 
 Silver iodate 
 AgIO3 
 3.2 x 10-8 
 Silver iodide 
 AgI 
 8.5 x 10-17 
 Strontium carbonate 
 SrCO3 
 5.6 x 10-10 
 Strontium fluoride 
 SrF2 
 4.3 x 10-9 
 Strontium sulfate 
 SrSO4 
 3.4 x 10-7 
 Zinc sulfide 
 ZnS 
 2.0 x 10-25 

21. Solving Solubility Problems
For the salt AgI at 25C, Ksp = 1.5 x 10-16
AgI(s)  Ag+(aq) + I-(aq) I C E O O +x +x x x
1.5 x = x2
x = solubility of AgI in mol/L = 1.2 x 10-8 M

22. Solving Solubility Problems
For the salt PbCl2 at 25C, Ksp = 1.6 x 10-5
PbCl2(s)  Pb2+(aq) + 2Cl-(aq) I C E O O +x
+2x x 2x
1.6 x 10-5 = (x)(2x)2 = 4x3
x = solubility of PbCl2 in mol/L = 1.6 x 10-2 M

23. Solving Solubility with a Common Ion
For the salt AgI at 25C, Ksp = 1.5 x 10-16
What is its solubility in 0.05 M NaI?
AgI(s)  Ag+(aq) + I-(aq) I C E O
0.05 +x
0.05+x x
0.05+x
1.5 x = (x)(0.05+x)  (x)(0.05)
x = solubility of AgI in mol/L = 3.0 x M

24. Precipitation and Qualitative Analysis

25. Complex Ions A Complex ion is a charged species composed of:
1. A metallic cation
2. Ligands – Lewis bases that have a lone electron pair that can form a covalent bond with an empty orbital belonging to the metallic cation

26. NH3, CN-, and H2O are Common Ligands

27. Coordination Number
Coordination number refers to the number of ligands attached to the cation
2, 4, and 6 are the most common coordination numbers
Coordination
number
Example(s) 2
Ag(NH3)2+ 4
CoCl Cu(NH3)42+ 6
Co(H2O) Ni(NH3)62+

28. Complex Ions and Solubility
AgCl(s)  Ag+ + Cl- Ksp = 1.6 x 10-10
Ag+ + NH3  Ag(NH3) K1 = 2.1 x 103
Ag(NH3)+ NH3  Ag(NH3) K2 = 8.2 x 103
AgCl + 2NH3  Ag(NH3)2+ + Cl-
K = KspK1K2