Chapter 19 – Acids and Bases
Read page 471 of your text book
Strong Electryolyte –
Weak Electrolyte –
Non-electrolyte Pg. 455-459 ChemStudy Handout
Equilibrium:
- no…
- balance …
- forward reaction…
17.1 Electrolytes: Strong and Weak
- aqueous solutions conduct if…
High conductivity =
Low conductivity =
Strong electrolytes –
Ex.
Weak electrolytes –
Ex.
17.2 Water: A very weak electrolyte
Ionization of water eqn:
Equilibrium constant expression:
or
K=
Kw =
Kw and its variation with temperature
Value of Kw is very big/very small.
In pure water concentration of H+
If Kw = 1.0 x 10-14
[H+] =
[OH-] =
1
= , <,
>
concentration of OH-
Read page 607-609 of your text book
concentrated / dilute
vs.
strong / weak
19.3 – What is pH?
- Water can act as a ________ or __________.
Add any notes/ideas/ understanding from pg. 608-609 to your notes on the previous page
from reading the ChemStudy handout – 17.3 Water – a very weak electrolyte.
To Be Completed in class -----------------------------------------------------------Conductivity Demo – see Handout
Categorize each of the following solutions:
Acid/Base/
Concentrate/
Solution
Salt/Molecular
dilute
0.10 M NaCl
0.010 M NaOH
5.0 M Ca(OH)2
12.0 M HCl
6.0 M CH3COOH
0.200 M KOH
0.5 M C2H5OH
2.0 M KNO3
0.10 M Ba(NO3)2
0.0010 M HBr
1.0 M C6H12O6
0.05 M HNO3
2
Strong/weak/
non electrolyte
Ionize/
dissociate
Understanding Ion Concentrations in Solution:
1) Given each of the following solutions, what are the concentrations of the ions present?
a. 1.00 M KBr
[K+] =
[Br-] =
b. 1.00 M Al(OH)3
[Al3+] =
[OH-] =
c. 3.00 M HBr
[H+] =
[Br-] =
d. 3.00 M CH3COOH
[H+] =
[CH3COO-] =
Draw a picture of each of the above solutions.
What kind of electrolyte is water? ____________ Draw a picture of what a beaker of water
looks like at the molecular level.
Read pg. 458-460
Concentrations of H+ and OH- in solution
Neutral solution –
If you add HCl to water the [H+] ____________;
Done
thus the [OH-] ___________
in class
because K =[ ] [ ] =
If 0.01 mol HCl is dissolved in 1 L of water
[H+] =
[OH-] =
Acid – a substance that produces an acidic solution when it is dissolved in water
Acidic:
[H+]
[OH-]
3
If you add NaOH to water the [OH-] ____________;
thus the [H-] ___________
Done
because K =[ ] [ ] =
in class
If 0.01 mol NaOH is dissolved in 1 L of water
[OH-] =
[H-] =
Base – A substance that produces a basic (alkaline) solution in water
Basic:
[H+]
[OH-]
Done
in class
If 0.0010 mol HCl is dissolved in 1.00 L of water
[OH-] =
[H-] =
If 0.10 mol NaOH is dissolved in 1.00 L of water
[OH-] =
[H-] =
Read pg 460-464
Acid-base Titration & Neutralization
HCl + NaOH 
HCl and NaOH in the same solution: Excess HCl
Suppose I add 0.090 moles of NaOH(s) to 0.100 L of 1.0 M HCl; What is the concentration of [H+] and [OH-]?
HCl and NaOH in the same solution: Excess NaOH
Suppose I add 0.101 moles of NaOH(s) to 0.100 L of 1.0 M HCl; What is the concentration of [H+] and [OH-]?
HCl and NaOH in the same solution: NO Excess
Suppose I add 0.100 moles of NaOH(s) to 0.100 L of 1.0 M HCl
Equivalence point 4
Titration Process –
Example: A base of known concentration is added to _________________________________
KEY:
At the equivalence point
Moles HCl =
equivalence point –
indicator –
end point –
STEPS:
1)
Done
in class 2)
3)
4)
Ex. If it takes 15.0 mL of an NaOH solution of unknown concentration to neutralize 10.0 mL of 0.100 M
HCl, what must be the concentration of the original NaOH solution?
More Titration Example Problems:
1) If it takes 19.5 mL of KOH solution to completely neutralize 20.2 mL of 0.150 M HCl, what is the
concentration of the original KOH solution?
2) If it takes 18.3 mL of Ca(OH)2 solution to completely neutralize 14.0 mL of 0.200 M HNO3, what is the
concentration of the original Ca(OH)2 solution?
3) 0.150 moles of HI are neutralized by 30.0 mL of NaOH, what is the concentration of the original NaOH
solution?
5
Neutralization Reactions:
Write the neutralization reaction for the following:
1) Solutions of nitric acid and lithium hydroxide are mixed.
Done
in class
2) Solutions of hydrofluoric acid (weak!) and potassium hydroxide are mixed.
Read pg. 610-614
pH and pOH
pH =
acid pH
base pH
Logarithmic scale means pH change = 1 is the same as a [H+] = _________
Ex. 19-2 What is the pH of a neutral solution at 298K (25°C)?
Answers:
a. pH = 2.00
b. pH = 5.52
c. pH = 8.93
Practice Problem #19:
a. [H+] = 1.0 x 10-2
b. [H+] = 3.0 x 10-6
Note: If you answered 5.07
for “c” that means you forgot
to convert [OH-] to [H+].
c. [OH-] = 8.2 x 10-6
pOH =
pH + pOH = ________
[H+]
10-7
7
pH
pOH
7
[OH-]
10-7
6
Ex. 19-3 An ordinary household ammonia cleaner is an aqueous solution of ammonia gas with a
hydroxide-ion concentration of 4.0 x 10-3 M. Calculate pOH and pH of a typical cleaner at 298K.
Calculating ion concentrations from pH
Ex. 19-4 What are [H+] and [OH-] in a healthy person’s blood that has a pH of 7.40? Assume
that the temperature is 298K.
Calculating the pH of solutions of strong acids and strong bases
Strong acids ionize _______.
If a bottle says 0.10 M HCl, then [H+] = ______, [Cl-] = _________.
Strong bases ______________(dissociate is the more appropriate term).
If a bottle says 0.10 M NaOH, then [Na+] = ______, [OH-] = _________.
To be completed in class-----------------------------------------------------------------------------
Calculating pH, [H+], [OH-], and pOH
pH = - log [H+]
(understanding logs)
[H+] = 10-pH
pH scale
0
14
7
7
Neutral
[H+] [OH-]
pH
Acidic
[H+] [OH-]
pH
Basic
[H+] [OH-]
pH
Calculating pH, pOH, [H+], [OH-]:
pH = - log [H+]
[H+] = 10-pH
pOH = - log [OH-]
[OH-] = 10-pOH
Solution
[H+]
[OH-]
Kw = 1.00 x 10-14 = [H+][OH-]
pH
pOH
Acidic/
Basic
0.010 M
HCl
0.10 M
KOH
0.0010 M
HBr
0.020 M HI
0.010 M
NaOH
0.01 M
Sr(OH)2
_____ M
HCl/KOH
_____ M
HNO3/KOH
_____ M
HI/LiOH
0.010 M
Ca(OH)2
___ M
Ba(OH)2
0.010 M
CH3COOH?
3.00
12.00
1.25
1.25
Summary Questions:
1) Which solution is twice as acidic as 0.010 M HCl , pH = 2.00?
a.
0.020 M HCl (pH = 1.70)
b. 0.10 M HCl (pH = 1.00)
c. 0.0010 M HCl (pH = 3.00)
2) Which solution has the highest pH?
a. 0.500 M HCl
b. 0.0020 M HNO3
c. 0.0300 M LiOH
3) How much more acidic is 0.100 M HCl (pH = 1.00) than a 0.0010 M HCl (pH = 3.00)?
a. 3x
b. 1/3x
c. 20x
d. 1/20 x e. 100x
f. 1/100 x
8
Diagram:
At any point:
K = [H+] [OH-]
14 = pH + pOH
At the neutral Line:
pH = 7 = pOH
Use a ruler to find other corresponding points.
Ex. pH = 3.3
[H+] = 5 x 10-4 M
[OH-] = 2 x 10-11
pOH = 10.7
and
pH = 12.4
[H+] = 4 x 10-13 M
[OH-] = 2.3 x 10-2
pOH = 1.6
=======================================================
Read pages 600-603, 605
Monoprotic and Polyprotic Acids
Acids can _________________________________. (ex. HCl and HF)
Acetic (ethanoic) acid, CH3COOH, has ______________ ionizable hydrogens.
Benzene, C6H6, has ______________ ionizable hydrogens.
Monoprotic Diprotic Triprotic Polyprotic –
Stepwise ionization of phosphoric acid:
H3PO4 + H2O 
______ + H2O 
______ + H2O 
9
Strength of Acids
Strong acids –
6 strong acids:
HCl + H2O  _____________
Single arrow means _____________________________.
Weak acid –
HC2H3O2 + H2O  ________________
Doublé arrow means ______________________.
Acid ionization constants
HCN + H2O  H3O+ + CNKeq =
Ka =
Note: numerator is the reactants/products.
Denominator is the reactants/products.
Weak acids:
[products] - large/small
[reactants - large/small
Thus Ka - large/small
Strong acids: [products] - large/small
[reactants - large/small
Thus Ka - large/small
Strengths of bases
Strong bases –
Ex.
Weak bases –
Ex.
10
To be completed in class-----------------------------------------------------------------------
Arrhenius Model
Acid – any substance that increases
the [H+] in solution
Strong Acids
Base – any substance that increases
the [OH-] in solution
Strong Bases
definition:
definition:
All Examples
All Examples
Ionization equations:
dissociation equation:
Weak Acids
Weak Bases
definition:
definition:
some Examples
some Examples
ionization equations:
dissociation eqns
ionization eqn:
Comparing [H+] (given Ka chart)
 How do the following [H+] compare? (Hint: Think about % ionization)
1. 0.10 M HCl
0.10 M HBr
2. 0.10 M HCl
0.10 M H2SO4
3. 0.10 M HNO3
0.10 M HF
4. 0.10 M CH3COOH
0.10 M HCN
 Rank the following in order of increasing [H+]
HF, HNO3, HCl, HNO2
H3PO4, HF, H2SO4, HI, HS-
11
Amphoteric Substances –
-
Properties of Acids and Bases
ACIDS
BASES
1.
1.
2.
3. turns litmus __________
3. turns litmus _________
4. phenolphthalein = _________
4. phenolphthalein = ________
pH scale
0
7
14
5.
==========================================================
Read pg. 598-599, 603-604
Bronsted-Lowry Model:
Acid –
Base –
Ex equation:
Conjugate acid –
Conjugate base –
Conjugate acid/base pair –
12
HF + H2O 
NH3 + H2O 
Amphoteric To be completed in class--------------------------------------------------------------------HCl
Proton-transfer Reactions:
1) HF(aq) + H2O(l)  F-(aq) + H3O+(aq)
2) HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq)
3) H2SO4(aq) + H2O(l)  _________ + _________
4) HCl(aq) + NH3(aq)  _________ + _________
5) H3O+(aq) + ClO4-(l)
6) CH3COOH(aq) + H2O(l)
HClO4 (aq) + H2O(l)
________ + ________
7) H2CO3 (aq) + H2O(l)  HCO3-(aq) + H3O+(aq)
CH3COOH
H+ + ClH+ + CH3COO-
* The stronger the acid, the
___________ the conjugate
base.
* The weaker the acids, the
___________ the conjugate
base.
* TREND: production of the
stronger/weaker acid and
stronger/weaker base is
favored.
(Note: the strong acid and the
strong base are always on
____________ side.)
The extent the reaction occurs
depends on the relative
strengths of the acids and
bases involved.
8) HSO3-(aq) + H3O+ (aq)  ________ + ________
9) CN- (aq) + HC2H3O2 (l)  HCN(aq) + C2H3O2-(aq)
10) HCN(aq) + _________  HF(aq) + _________
Questions:
1) What’s the conjugate base of
HPO42-? _________
2) HSO4- is the conjugate base of
what? ___________
It’s the conjugate acid of
what? __________
* Now go back up and circle the side favored.
Q – Would #2 or #4 have a greater tendency to form products? ______
13
Lewis Model
Acid –
Base –
Ex.
HCN + NH3 
AlCl3 + NH3 
Excess Problems:
Key: 1) Acid/Base excess problems are really just limiting reactant problems.
2) When acids and bases react the net ionic equation is: ________________
1) If 0.100 moles of KOH and 0.100 moles of HCl are mixed, what’s the pH of the resulting
mixture?
2) If 0.100 moles of KOH and 0.150 moles of HCl are mixed in a total volume of 2.00 L, what’s
the pH of the resulting mixture?
3) If 13.0 mL of 0.200 M LiOH and 20.0 mL of 0.150 M HI are mixed, what’s the [H+], [OH-],
and pH of the resulting mixture?
4) If 13.0 mL of 0.200 M Ca(OH)2 and 20.0 mL of 0.150 M HI are mixed, what’s the [H+], [OH-],
and pH of the resulting mixture?
Summary of steps for excess problems:
1) Calculate moles of H+ and OH2) Determine the number of moles of excess reactant
3) Divide the number of moles of excess reactant by total volume to determine the
concentration of excess reactant.
5) To calculate [H+], [OH-], or pH …
Kw = 1.00 x 10-14 = [H+] [OH-]
pH = - log [H+]
REVIEW - differentiating between titration and excess problems
Titration
14
Excess