Acids & Bases
Chemistry 6.0
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
Properties of Acids and Bases:
Acid
Base
(alkali)
Reactions
Electrical
with Metals Conductivity
Taste
Touch
sour
looks like
water,
burns,
stings
Yesproduces
H2 gas
electrolyte
in solution
bitter
looks like
water,
feels
slippery
No
Reaction
electrolyte
in solution
Indicators: Turn 1 color in an acid
and another color in a base.
A.
Litmus Paper: Blue and Red
An aciD turns blue litmus paper reD
A Base turns red litmus paper Blue.
B. Phenolphthalein: colorless in an acid and
pink in a base
C.
D.
pH paper: range of colors from acidic to
basic
pH meter: measures the concentration
of H+ in solution
Reactions
Neutralization: A reaction between an
acid and base. When an acid and base
neutralize, water and a salt (ionic solid)
form.
Acid + Base → Salt + Water
Ex) HCl + NaOH → NaCl + HOH
Reactions
Acids and Metals
– HA + M  H2 + MA
A = anion
M = metal
– 2HCl + Mg  H2 + MgCl2
Acids and Carbonates
– HA + MCO3  MA + CO2 + H2O
– HCl + Li2CO3  2LiCl + CO2 + H2O
Arrhenius Definition (1884):
A. An acid dissociates in water to produce more
hydrogen ions, H+.
HCl  H+1 + Cl-1
B. A base dissociates in water to produce more
hydroxide ions, OH-.
NaOH  Na+1 + OH-1
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
Bronsted-Lowry Definition (1923):
A. An acid is a substance that can donate hydrogen ions.
Ex) HCl → H+ + Cl–
–
–
Hydrogen ion is the equivalent of a proton.
Acids are often called proton donors.
Monoprotic (HCl), diprotic (H2SO4) , triprotic (H3PO4)
B. A base is a substance that can accept hydrogen ions.
Ex) NH3 + H+ → NH4+
–
Bases are often called proton acceptors.
C. Advantages of Bronsted-Lowry Definition
•Acids and bases are defined independently of how
they behave in water.
•Focuses solely on hydrogen ions.
Hydronium Ion:
Hydronium Ion – H3O+ This is a complex ion
that forms in water.
H+1 + H2O  H3O+1
To more accurately portray the Bronsted-Lowry,
the hydronium ion is used instead of the
hydrogen ion.
STRONG Acid/Base versus
WEAK Acid/Base
Strength refers to the % of molecules that form IONS.
A strong acid or base will completely ionize (>95%
as ions). This is represented by a single ()
arrow.
HNO3 + H2O  H3O+ + NO3A weak acid or base will partially ionize (<5% as
ions). This is represented by a double (↔) arrow.
HOCl + H2O
↔
H3O+ + ClO-
HF < HCl < HBr < HI
increasing strength
7 Strong Acids
HNO3
H2SO4
HClO4
HCl
HI
HClO3
HBr
8 Strong Bases
LiOH
NaOH
RbOH
CsOH
Sr(OH)2
Ba(OH)2
KOH
Ca(OH)2
Strength vs.
Concentration
• Strength refers to the percent of
molecules that form ions
• Concentration refers to the amount of
solute dissolved in a solvent. Usually
expressed in molarity.
• See “Acids: Concentration vs. Strength”
Conjugate Acid-Base Pairs: A pair of
compounds that differ by only one
hydrogen ion
A. Acid donates a proton to become a
conjugate base.
B. Base accepts proton to become a conjugate
acid.
•
•
A strong acid will have a weak conjugate
base.
A strong base will have a weak conjugate
acid.
Acid (A), Base (B),
Conjugate Acid (CA), Conjugate Base (CB)
NH3 +
H2O
↔ NH4+ +
OH-
HCl +
H2O
↔ Cl-
H3O+
B
A
A
B
CA
CB
+
CB
CA
• Base and Conjugate Acid are a Conjugate
Pair.
• Acid and Conjugate Base are a Conjugate
Pair.
AciDonates & Bases accept
1. H2O
B
+
H 2O
↔
A
B
B
4. OH− + H3O+
B
A
HSO4−
OH−
CB
+
H 2O
CB
3. HSO4− + H2O ↔
A
+
CA
2. H2SO4 + OH− ↔
A
H3O+
SO4−2
CA
+
H3O+
CB
↔
CA
H 2O + H 2 O
CA
CB
Ionization of Acids & Bases
• H2SO4  2 H+ + SO4-2
– Sulfuric acid
• H3PO3 
3 H+ + PO3-3
– Phosphorous acid
• Ca(OH)2  Ca+2 + 2 OH-1
– Calcium hydroxide
The Self-ionization of Water & 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)
Keq = equilibrium constant = [H3O+] [OH-]
Because reactants and products are at equilibrium, liquid water is
not included in the equilibrium expression
@ 25C, [H3O+] = 1 x 10-7 M and [OH-] = 1 x 10-7 M
Kw = ion product constant or equilibrium constant for water
Kw = [H3O+] [OH-] = 1 x 10-14 M2
1.0 x 10-14 M2 = [1.0 x 10-7 M] [1.0x10-7 M]
1.0 x 10-14 =
[H3O+]
[OH-]
Acids: [H3O+] > 1 x 10-7 M
Bases: [OH-] > 1 x 10-7 M
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?
Kw = [H3O+] [OH-]
1.0 x 10-14 M2 = [4.0 x 10-8 M] [OH-]
2.5 x 10-7 M = [OH-]
slightly basic
The pH scale (1909): the power of Hydrogen
A. Measure of H3O+ in solution.
B. pH = -log[H3O+]
C. Range of pH: 0-14
pH < 7: acid
pH > 7: base
pH = 7: neutral
D. pOH = -log[OH-]
E. pH + pOH = 14
D. pH = -log [H3O+]
E. [H3O+] [OH-] = 1.0 x 10-14
F. pH + pOH = 14
pH
7
1
14
OH-
H+
H+
OH-
14
1
pH
[H3O+]
[OH-]
14
1x10-14
1x100
13
1x10-13
1x10-1
12
1x10-12
1x10-2
11
1x10-11
1x10-3
10
1x10-10
1x10-4
9
1x10-9
1x10-5
8
1x10-8
1x10-6
7
1x10-7
1x10-7
6
1x10-6
1x10-8
5
1x10-5
1x10-9
4
1x10-4
1x10-10
3
1x10-3
1x10-11
2
1x10-2
1x10-12
1
1x10-1
1x10-13
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[8.7x10-4M]
 Calc
Answer = 3.0604807474
 Sig Fig pH = 3.06
Acid-Base Titration
1. An acid-base titration is a carefully controlled
neutralization reaction or redox which can
determine 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. Titration curve: graph that
shows how pH changes
during a titration.
4. An indicator, usually
phenolphthalein, is
used in a titration.
•
Colorless in an acid,
pink in a base.
5. The point at which
enough standard
solution is added to
neutralize the unknown
solution is called the
equivalence point.
6. The point at which the indicator
changes color is called the endpoint.
7. Therefore: [H+] = [OH-] at the
equivalence point
Ex) A volume of 50.0 mL of 0.150M sodium
hydroxide neutralizes 30.0mL of a sulfuric acid
solution. What is the concentration of the
sulfuric acid solution?
H2SO4 + 2 NaOH 
Na2SO4 + 2 HOH
Note: Mole ratio between acid an base in not 1:1
Mb = 0.125M