Identifying Acids and Bases
• Acids
• Acid (anhydrides)
• Bases
contains H+ ions as the cation,
with and other element as the
anion
Non-metal oxide
Contains OH- as the anion
H2SO4
HI
P2O5
Ca(OH)2
Combined with a cation
• Base (anhydrides)
• Salts
A metal with oxygen
Ionic compound
Formed from a cation and an
anion
Metal and non-metal
Al2O3
Mg F2
KCl
LiBr
Acid / Base Chemistry
•Hydrogen ion concentration = [H+]
•Hydroxide ion concentration = [OH-]
•Pure H20 – neutral substance –
– ph=7 and [H+]=[OH-]
•H2O will self-dissociate
– H20 > H+ + OH– Note: the number of H2O molecules that will self dissociate is very
small; only 2 molecules per a billion, therefore [H2O] is unchanged.
Acid / Base Chemistry
- Kw - is the ion product constant for
water
- Kw = 1.0 x 10-14 M2
Kw= [H+] [OH-]
FOR H2O
:Kw= [1.0 x 10-7 M][1.0 x 10-7M]
- there is an indirect relationship
between [H+] and [OH-]
Acid / Base Chemistry
•Calculate [OH-] if [H+] is 1.0 x 10-2 M
• Kw= [H+] [OH-]
• [OH-]= Kw
•
[H+]
= 1.0 x 10-14M2
1.0 x 10-2M
• [OH-]= 1.0 X 10 –12 M
Acid / Base Chemistry
•Calculate [H+] if [OH-] is 6.5 x 10-11 M
• Kw= [H+] [OH-]
• [H+]= Kw
[OH-]
= 1.0 x 10-14M2
6.5 x 10-11M
• [H+]=
• [H+] will tell us if a soln is acidic or
basic.
Acidic
solutions
Neutral
solutions
Basic
solutions
pH= 1- 6
-1
-6
[H+]= 1.0 x 10 M – 1.0 x 10 M
[H+] > [OH-]
pH= 7
[H+] = [OH-]
-7
1.0 x 10 M for both
pH= 8 -14
-8
-14
[H+]= 1.0 x 10 M – 1.0 x 10 M
[H+] < [OH-]
Acid / Base Chemistry
• If [H+]= 1.0 x 10-9M, will the solution be
basic or acidic?
• Basic
• Why?
• because the pH= 9 and this solution
contains less [H+] than [OH-]
Acid / Base Chemistry
• If [OH-]= 2.63 x 10-4M, will the solution
be basic or acidic or neutral?
•
• Why?
Acid / Base Formulas
•
•
•
•
•
pH= -log [H+]
pOH= -log [OH-]
pH + pOH =14
[H+] = antilog (-pH)
[OH-] = antilog (-pOH)
• How to use the calculator!!
• Calculate the pH of a solution with [H+] =
0.001 M. Is this acidic, basic, or neutral?
Acid / Base Formulas
• Calculate the pH of a solution with [OH-] = 7.9
x 10-3 M. Is this acidic, basic, or neutral?
• Calculate the pH of a solution with [H+] =
4.2 x 10-6 M. Acidic, basic, or neutral?
What is the [OH-]?
Acid / Base Formulas
• A solution with a pH of 9.1 has what [H+]?
– 2nd log –9.1 ENTER
• What is the [OH-]?
• What is the pOH?
Scientists Who Define Acids /
Bases
•Arrhenius:
Acids: Any substance which releases
H+ ion in water solution.
Bases: Any substance which releases
OH- ion in water solution.
Scientists Who Define Acids /
Bases
•Bronsted - Lowry:
Acids: Any substance which
donates a proton.
Bases: Any substance which accepts
a proton.
Acids, Bases, and Their
Conjugates
•Water is amphoteric – has basic +
acidic properties.
•Conjugate Acid: Substances formed in a
reaction when a base gains a H+
•Conjugate Base: Substances formed in a
reaction when an acid donates H+
Acids, Bases, and Their Conjugates
• NH3 + H2O
-- NH4+ + OH-
• HCl + H2O
--->
Acids, Bases, and Their Conjugates
• CO3-2 + H2O
---> HCO3- + OH-
• Ca(OH)2 + 2HNO3 --> Ca(NO3)2 + 2HOH
Identifying monoprotic, diprotic, and triprotic:
monoprotic:
HCl
H+ + Cl-
diprotic:
H2SO4
H+ + HSO4-1
HSO4-1
H+ + SO4-2
triprotic:
H3PO4
H2PO4-1
HPO4-2
H+ + H2PO4-1
H+ + HPO4-2
H+ + PO4-3
Strengths of Acids and Bases
• Strong acids and bases will completely dissociate
ex. HCl --> H+ + Cl• The six strong acids - HCl, HBr,
• HI, H2SO4, HNO3, HClO4
• All others are weak.
• Strong Bases: Groups I
• and II with OH- except Be
Strengths of Acids and Bases
•Weak acids and bases slightly
dissociate
ex. HClO <--> ClO- + H+
Electrolytes and Non-Electrolytes
•Strong Electrolytes:
- Compounds that conduct electricity in
aqueous solution
- Substances that completely dissociate
- Strong acids and bases
- Soluble salts
Electrolytes and NonElectrolytes
•Weak Electrolytes:
- Slight electron conductivity
- Slight dissociation in aqueous
- Weak acids and bases
- Insoluble salts if in molten state
Electrolytes and NonElectrolytes
•NonElectrolytes:
- Don’t conduct electricity
- No ions to carry current
- Organic, molecular
Examples of Electrolytes and Nonelectrolytes:
• H2S03
• weak acid/weak elect.
• CsOH
• strong base/strong elect.
• HCl04
• strong acid/strong elect.
• C6H1206
• nonelectrolyte- covalent, molecular, organic b/c
carbon
Examples of Electrolytes and Nonelectrolytes:
• Al(OH)3
• weak base/weak electrolyte
• HF
• weak acid/weak electrolyte
• CCl4
• nonelectrolyte- molecular compound
• NaN03
• soluble salt/strong electrolyte
• S03
• acid anhydride/weak electrolyte
Neutralization Reactions:
General Equation:
• Acid + Base
Salt + Water
• HCl + NaOH
NaCl + HOH
Acid
Base
Salt
Water
Neutralization Reactions:
Titration: Analytical method used to determine the
concentration of acids and bases in a neutralization
reaction.
1. Measured volume of an acid or
base with unknown
concentration. Put in Erlenmeyer.
2. Add a few drops of indicator to
the Ernlenmeyer.
3. A measured volume of titrant is
delivered into the flask through a
buret (base or acid)
4. Concentration of the titrant is
known –Standard Solution.
5. Neutralization occurs when
indicator is revealed  End
Point
6. Equivalence Point
MOL ACID = MOL BASE
Titration Curve
Neutralization practice problems:
1. What volume of calcium hydroxide in a 3.0
M solution is needed to neutralize 45.0 mL
of 2.6 M perchloric acid?
Neutralization practice problems:
2. Determine the [Ba(OH)2] solution if 300.0 mL
was titrated to neutrality with 220.5 mL of
6.0 M solution of phosphoric acid?
Neutralization practice problems:
1. What volume of calcium hydroxide in a 3.0 M solution is needed to neutralize
45.0 mL of 2.6 M perchloric acid?
M
CR
M
vol
mol
mol
vol
G: 45 mL
Ca(OH)2 + HCl04
2 HOH + Ca(Cl04)2
2.6 M HCl04
0.45 L HCl04 x 2.6 mol HCl04 x 1 mol Ca(OH)2 x 1 L Ca(OH)2
3.0 M Ca(OH)2
1 L Ca(OH)2
2 mol HCl04
3 mol Ca(OH)2
U: ? vol Ca(OH)2
2. Determine the [Ba(OH)2] solution if 300.0 mL was titrated to neutrality with
220.5 mL of 6.0 M solution of phosphoric acid vol M mol CR mol
G: 220.5 mL
6.0 M H3P04
3Ba(OH)2 + 2H3P04
Ba3(P04)2 + 6HOH
0.2205 L H3P04 x 6.0 mol H3P04 x 3 mol Ba(OH)2
300.0 mL Ba(OH)2
1 L H3P04
U: ? M Ba(OH)2
2 mol H3P04
= 1.985 mol Ba(OH)2
1.985 mol Ba(OH)2
0.300L Ba(OH)2
= 6.62 M Ba(OH)2
Dissociation examples
Acid/Base Chemistry
• Hydrogen ion
concentration= [H+]
• Hydroxide ion
concentration= [OH-]
• Pure HOH= neutral
substance.
• Kw is constant for
water. [Kw= 1E-14
M2]
More Acid/Base Chemistry
• Kw = [1x10-7 M][1x10-7
M] (Kw=[H+][OH-])
• Most other substances are
not neutral
• Indirect relationships
between [H+] and [OH-]
• [H+] will tell us if solution
is Acidic or basic.
Strengths of Acids and Bases
•Strong Acids: HCl, HI, HBr,
H2SO4, HNO3, HClO4
•Strong Bases: Groups I and II with
OH- except Be
Identifying Electrolytes and Nonelectrolytes:
Strong Electrolytes:
-compounds that conduct electricity in aqueous solutions
-substance that completely dissociate
-strong acids and bases
-soluble salts
Weak Electrolytes:
-slight electrical conduct
-slight dissociation in aqueous solution
-conducts in molten state
-weak acids and bases
-insoluble salts (if in molten state)
Nonelectrolytes:
-don’t conduct electricity
-no ions to carry current
-organic, molecular
Neutralization
•Acid + Base > Salt + H2O
•Neutralization is found using titration
•Titration: Analytical method used to
determine the concentration of acids,
bases in a neutralization reaction.
Neutralization reactions
• Products always end
in a salt and water.
• Acid + Base = Salt +
HOH
• Titration- Analytical
method used to
determin the
concentration of acids
in a neutralization
reaction.
Theory