Acids & Bases
1. Properties of Acids and Bases:
Acid
Base
Taste
Touch
sour
looks like
water,
burns,
stings
bitter
looks like
water,
feels
slippery
Reactions
Electrical
with Metals Conductivity
Yesproduces
H2 gas
electrolyte in
solution
(breaks up
into ions)
No
Reaction
electrolyte in
solution
(breaks up
into ions)
2. Indicators: Turn 1 color in an acid and
another color in a base.
A. Litmus Paper: An aciD turns blue litmus paper reD
A Base turns red litmus paper Blue.
B. Phenolphthalein: colorless in an acid/pink in a base
C. pH paper: range of colors from acid to basic
(pH acids: 1-6.9 bases: 7.1 -14 neutral: 7.0)
D. pH meter: measures the concentration of H+ in
solution
3. Neutralization: A reaction between an acid and
base. When an acid and base neutralize, salts
form. “Salts” are any ionic compound formed
from the metal cation of the base and the anion
of the acid.
Acid + Base → Salt + Water
Ex) HCl + NaOH → NaCl + HOH
4. Arrhenius Definition:
A. An acid dissociates in water to produce
hydrogen ions, H+.
B. A base dissociates in water to produce
hydroxide ions, OH-.
C. Problems with Definition:
• Restricts acids and bases to water solutions.
• Oversimplifies what happens when acids
dissolve in water.
• Does not include certain compounds that have
characteristic properties of acids & bases.
Ex) NH3 (ammonia) doesn’t fit
5. BrØnsted-Lowry Definition:
A. An acid is a substance that can donate
hydrogen ions. Ex) HCl → H+ + ClB. A base is a substance that can accept
hydrogen ions. Ex) NH3 + H+ → NH4+
C. Advantages of BrØnsted-Lowry Definition
•Acids and bases are defined independently of how
they behave in water.
•Focuses solely on hydrogen ions.
D. Hydrogen ion is the equivalent of a proton.
Therefore, acids are often called proton donors and
bases are called proton acceptors.
6. Hydronium Ion:
A. Hydronium Ion – H3O+ This is a complex
that forms in water.
B. To more accurately portray the BronstedLowry, the hydronium ion is used instead of
the hydrogen ion.
C. Amphoteric: A substance that can act as either
an acid or a base.
Ex.) Water - can gain or lose a H+
7. Conjugate Acid-Base Pairs:
A pair of compounds that differ by only one
hydrogen ion
A. When an acid loses a hydrogen ion, it
becomes its conjugate base.
B. When an base gains a hydrogen ion, it
becomes its conjugate acid.
Acid (A), Base (B),
Conjugate Acid (CA), Conjugate Base (CB)
NH3 +
B
HCl +
A
H2O
A
H2O
B
↔ NH4+ +
OH-
↔ Cl-
H3O+
CA
CB
+
CB
CA
• A strong acid will have a weak conjugate base.
• A strong base will have a weak conjugate acid.
STRONG Acid/Base
C. A strong acid or base will completely
dissociate (break apart) in water. This is
represented by a single () arrow.
HNO3  H+ + NO3NaOH  Na+ + OH-
WEAK Acid/Base
D. A weak acid or base will partially
dissociate in water. This is represented by
a double (↔) arrow.
CH3COOH ↔ H+ + CH3COONH4OH ↔ NH4+ + OH-
8. Naming Acids Review:
A. Binary – H +one anion Prefix “hydro”+ anion name +“ic”acid
Ex) HCl
Ex) H3P
hydrochloric acid
hydrophosphoric acid
B. Tertiary – H + polyatomic anion
(oxo)
Ex) H2SO4
Ex) H2SO3
no Prefix “hydro”
end “ate” = “ic” acid
end “ite” = “ous” acid
sulfuric acid
sulfurous acid
15-2 The Self-ionization of Water and pH
1. Water is amphoteric, it acts as both an acid and a
base in the same reaction.
Ex) H2O(l) + H2O(l) ↔ H3O+(aq) + OH-(aq)
2. In pure water at 25C, both hydronium ions and
hydroxide ions are found at concentrations of
1 x 10-7 M. Because they are at equilibrium and
you do not include liquid water in the equilibrium
expression, Keq or Kw (water) can be expressed as
follows:
A. Formula for Kw = [H3O+] [OH-]
+
O]
A. Formula for Kw = [H3
[OH ]
1.0 x 10-14 M = [1.0 x 10-7 M] [1.0x10-7 M]
1.0 x 10-14 M = [H3O+] [OH-]
B. Using Kw in calculations:
If the concentration of H3O+ in the
blood is 4.0 x 10-8 M, what is the concentration of OH ions in the
blood? Is blood acidic, basic or neutral?
1.0 x 10-14 M = [H3O+] [OH-]
1.0 x 10-14 M = [4.0 x 10-8 M] [OH-]
4.0 x 10-8 M
2.5 x 10-7 M =
slightly basic
4.0 x 10-8 M
[OH-]
3. The pH scale:
A. Used to determine if something is an acid or
a base. A way to express H3O+ concentration
based on logarithms. pH changes by a factor
of 10.
Ex) 10,000 = 104 therefore log 10,000 = 4
0.001 = 10-3 therefore log 0.001 = -3
B. pH 1-6.9: acid
pH 7.1-14: base
pH of 7.0: neutral
D. pH = -log [H3O+]
E. [H3O+] [OH-] = 1.0 x 10-14M
F. pH + pOH = 14
OH-
H3O+
OHH3O+
EQUAL
pH
14
13
12
11
10
9
8
7
6
5
4
3
2
1
[H3O+]
[H3O+]
[OH-]
[OH-]
1x10-14
.00000000000001
1x100
1
1x10-13
.0000000000001
1x10-1
.1
1x10-12
.000000000001
1x10-2
.01
1x10-11
.00000000001
1x10-3
.001
1x10-10
.0000000001
1x10-4
.0001
1x10-9
.000000001
1x10-5
.00001
1x10-8
.00000001
1x10-6
.000001
1x10-7
.0000001
1x10-7
.0000001
1x10-6
.000001
1x10-8
.00000001
1x10-5
.00001
1x10-9
.000000001
1x10-4
.0001
1x10-10
.0000000001
1x10-3
.001
1x10-11
.00000000001
1x10-2
.01
1x10-12
.000000000001
1x10-1
.1
1x10-13
.0000000000001
H. Significant Digits Rule
The number of digits AFTER THE
DECIMAL POINT in your answer should
be equal to the number of significant digits
in your original number.
Ex -log[8.7 x 10-4 M]
– Calc Answer = 3.0604807474
– Sig Fig pH = 3.06
Example #1: [H3O+] = 7.3 x 10-5 M
What is the pH value?
Is it an acid, base or neutral?
Which equation should you use?
1.0 x 10-14 = [H3O+] [OH-]
OR
pH = -log [H3O+]
pH = -log [7.3 x 10-5M]
pH = 4.14
ACID
Example #2: [OH-] = 5.0 x 10-2 M
What is the [H3O+]? What is the pH value?
Is it an acid, base or neutral?
Which equation should you use?
1 x 10-14 = [H3O+] [OH-]
OR
pH = -log [H3O+]
1 x 10-14M = [H3O+] [5.0 x 10-2M]
2.0 x 10-13M = [H3O+]
pH = -log [2.0 x 10-13M]
pH = 12.70
basic
Ionization of Acids & Bases
• H2SO4  2 H+ + SO4-2
– Sulfuric acid donates 2 H+ ions per mole
– This is called a “diprotic” acid
• H3PO3 
3 H+ + PO3-3
– Phosphorous acid donates 3 H+ ions per
mole. This is called a “triprotic acid”
• Ca(OH)2 
Ca+2 + 2 OH-1
– Calcium hydroxide dissociates into 2 OHions per mole
15-3 Acid-Base Titration
1. An acid-base titration is a
carefully controlled
neutralization reaction which can
determine the concentration [ ]
of an unknown solution.
2. To determine the concentration
of an unknown substance, a
standard solution is needed.
This solution has a known
concentration.
3. An indicator, usually
phenolphthalein, is used
in a titration.
4. The point at which
enough standard
solution is added to
neutralize the unknown
solution is called the
equivalence point.
5. The point at which the
indicator changes color
is called the endpoint.
6. Therefore: [H3O+] = [OH-] at the equivalence
point (which is usually the endpoint)
Volume (acid) Conc.(acid) = Volume (base) Conc.(base)
VaMa = VbMb
(L) x Moles = (L) x Moles
Liter
Liter
moles of H3O+ = moles of OH-
HCl (a) = NaOH (b)
Ex #1) Solutions of sodium hydroxide are used to unclog
drains. A 43.0 mL volume of sodium hydroxide was
titrated with 32.0 mL of 0.100 M HCl. What is the
molarity of the sodium hydroxide solution? Write the
equation.
HCl + NaOH → NaCl + H2O
VaMa = VbMb
(32.0 mL)(0.100 M HCl) = (Mb)(43.0 mL)
43.0 mL
43.0 mL
0.0744 M
= Mb
Ex #2) A volume of 25.0 mL of 0.120 M sulfuric acid
neutralizes 40.0 mL of a sodium hydroxide solution. What
is the concentration of the sodium hydroxide solution?
H2SO4 + 2NaOH  Na2SO4 + 2HOH
Note: sulfuric acid has 2 H+ per mole of acid
Therefore you need to multiply the acid side by a factor of 2
VaMa x 2 = VbMb
(25.0 mL) (0.120 M) x 2 = (40.0 mL) x Mb
Mb = 0.150 M
Ex #3) 24.9 mL of 2.88 M calcium hydroxide completely
neutralizes 38.9 mL of a hydrobromic acid solution.
What is the molarity of the hyrdobromic acid?
Ca(OH)2 + 2HBr  CaBr2 + 2HOH
Note: there are 2 hydroxide ions per mole of base
Therefore you need to multiply the base side by a factor of 2
VaMa = VbMb x 2
(38.9 mL) x Ma = (24.9 mL) (2.88 M) x 2
Ma = 3.69 M