Acids and Bases
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Topics to be covered
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Acids and Bases
Arrhenius definition
Bronsted-Lowry definition
pH
Strong vs weak acids
Neutralization reactions
Some Properties of Acids
 Produce H+ (as H3O+) ions in water (the hydronium ion is a
hydrogen ion attached to a water molecule)
 Taste sour
 Corrode metals
 Electrolytes
 React with bases to form a salt and water
 pH is less than 7
 Turns blue litmus paper to red “Blue to Red A-CID”
Some Properties of Bases
 Produce OH- ions in water
 Taste bitter, chalky
 Are electrolytes
 Feel soapy, slippery
 React with acids to form salts and water
 pH greater than 7
 Turns red litmus paper to blue
“Basic Blue”
Acid Nomenclature Review
Anion
Ending
No Oxygen
Acid Name
-ide
hydro-(stem)-ic acid
-ate
(stem)-ic acid
-ite
(stem)-ous acid
w/Oxygen
An easy way to remember which goes with which…
“In the cafeteria, you ATE something ICky”
Acids and Bases: Theory
Arrhenius theory of acids
Arrhenius definition of an acid: any
compound that contains hydrogen and
produces H+ (H3O+ when reacts with
water) ions when dissolved in water.
A strong acid is a water-soluble compound
that completely dissociates to give H3O+
ions.
A weak acid is a water-soluble compound
that dissociates only partially, producing
few H3O+ ions.
Acids and Bases: Theory
Arrhenius theory of acids
A strong acid is a water-soluble compound
that completely dissociates to give H3O+
ions.
A weak acid is a water-soluble compound
that dissociates only partially, producing
few H3O+ ions.
Rafa Muñoa
Lizardi Institutua
Zarautz
Acids and Bases: Theory
Arrhenius theory of bases
Arrhenius definition of a base: any
compound that contains a metal and
hydroxide (OH-) group produces OH(hydroxide) ions when dissolved in water.
All hydroxides are strong bases because
their dissociation reaction go essentially to
completion.
Acids and Bases: Theory
Bronsted-Lowry theory of acids
and bases
They proposed that acids and
bases can be defined in terms of
their ability to transfer protons.
An acid is a substance
(molecule or ion) that can
transfer protons to another
substance.
A base is a substance than can
accept a proton.
Acids and Bases: Theory
Bronsted-Lowry theory of acids and
bases
An acid and a base always work
together to transfer a proton.
In other words, a substance can
function as an acid only if another
substance simultaneously behaves
as a base.
Acids and Bases: Theory
Bronsted-Lowry theory of acids and
bases
Some substances can act as an acid in
one reaction and as a base in
another.
For example, H2O is a Bronsted-Lowry
base in its reaction with HCl and a
Bronsted-Lowry acid in its reaction
with NH3.
Those substances are called
amphoteric.
Acids and Bases: Theory
Bronsted-Lowry theory of acids and
bases
To be a Bronsted-Lowry acid, a molecule
or ion must have a hydrogen atom that
it can lose as H+ ion.
To be a Bronsted-Lowry base, a molecule
or ion must have a nonbonding pair of
electrons that it can use to bind the H+
ion.
ACID-BASE THEORIES
The Brønsted definition means NH3 is a BASE in
water — and water is itself an ACID
NH3
Base
+
H2O
Acid
NH4+ + OHAcid
Base
Conjugate Pairs
Some Common Acids
HCl
hydrochloric acid
HNO3
nitric acid
H3PO4
phosphoric acid
H2SO4
sulfuric acid
CH3COOH
acetic acid
Learning Check AB3
Give the names of the following
A. HBr (aq)
1. bromic acid
2. bromous acid
3. hydrobromic acid
B. H2CO3
1. carbonic acid
2. hydrocarbonic acid
3. carbonous acid
Solution AB3
A. HBr
3. hydrobromic acid
The name of a nonoxy acid begins with the
prefix hydro- and ends with -ic acid. In a
nonoxy acid, the negative anion end in -ide.
B. H2CO31. carbonic acid
The name of an oxyacid is named with the
stem of the anion (carbonate) changed to
-ic acid
Learning Check!
Label the acid, base, conjugate acid, and
conjugate base in each reaction:
HCl + OH-  Cl- + H2O
Acid
Base
Conj.
Base
Conj.
Acid
H2O + H2SO4  HSO4- + H3O+
Base
Acid
Conj.
Base
Conj.
Acid
Some Common Bases
NaOH
sodium hydroxide
KOH
potassium hydroxide
Ba(OH)2
________________________
Mg(OH)2
________________________
Al(OH)3
aluminum hydroxide
Learning Check AB4
Match the formulas with the names:
A. ___
HNO2
1) hydrochloric acid
B. ___
Ca(OH)2
2) sulfuric acid
C. ___
H2SO4
3) sodium hydroxide
D. ___
HCl
4) nitrous acid
E. ___
NaOH
5) calcium hydroxide
LecturePLUS Timberlake
Solution AB4
Match the formulas with the names:
A. _4__ HNO2
1) hydrochloric acid
B. _5__ Ca(OH)2 2) sulfuric acid
C. _2__ H2SO4
3) sodium hydroxide
D. _1__ HCl
4) nitrous acid
E. _3__
5) calcium hydroxide
NaOH
Learning Check AB5
Acid, Base
or Salt
Name
CaCl2
______
_________________
KOH
______
_________________
Ba(OH)2 ______
_________________
HBr
______
_________________
H2SO4
______
__________________
Solution AB5
Acid, Base
or Salt
Name
CaCl2
salt
calcium chloride
KOH
base
potassiuim hydroxide
Ba(OH)2 base
barium hydroxide
HBr
acid
hydrobromic acid
H2SO4
acid
sulfuric acid
pH Scale
pH
 The Power of Hydrogen
 Measures the acidity or basicity of a solution
 pH = -log[H+]
 [H+] = 10-pH
 pOH = -log[OH-]
 [OH-] = 10-pOH
Calculating the pH
pH = - log [H+]
(Remember that the [ ] mean Molarity)
Example: If [H+] = 1 X 10-10
pH = - log 1 X 10-10
pH = - (- 10)
pH = 10
Example: If [H+] = 1.8 X 10-5
pH = - log 1.8 X 10-5
pH = - (- 4.74)
pH = 4.74
Try These!
pH = - log [H+]
Find the pH of these:
pH = - log 0.15
1) A 0.15 M solution of
pH = - (- 0.82)
Hydrochloric acid
pH = 0.82
2) A 3.00 X 10-7 M
solution of Nitric
acid
pH = - log 3 X 10-7
pH = - (- 6.52)
pH = 6.52
pH calculations – Solving for H+
If the pH of Coke is 3.12, [H+] = ???
Because pH = - log [H+] then
- pH = log [H+]
Take antilog (10x) of both
sides and get
10-pH = [H+]
[H+] = 10-3.12 = 7.6 x 10-4 M
*** to find antilog on your calculator, look for “Shift”
or “2nd function” and then the log button
pOH
• Since acids and bases are
opposites, pH and pOH are
opposites!
• pOH does not really exist, but it is
useful for changing bases to pH.
• pOH looks at the perspective of a
base
pOH = - log [OH-]
Since pH and pOH are on opposite
ends,
pH + pOH = 14
What is the pH of a 2 x 10-3 M HNO3 solution?
HNO3 is a strong acid – 100% dissociation.
Start 0.002 M
HNO3 (aq) + H2O (l)
End 0.0 M
0.0 M
0.0 M
H3O+ (aq) + NO3- (aq)
0.002 M 0.002 M
pH = -log [H+] = -log [H3O+] = -log(0.002) = 2.7
What is the pH of a 1.8 x 10-2 M Ba(OH)2 solution?
Ba(OH)2 is a strong base – 100% dissociation.
Start 0.018 M
Ba(OH)2 (s)
End 0.0 M
0.0 M
0.0 M
Ba2+ (aq) + 2OH- (aq)
0.018 M 0.036 M
pH = 14.00 – pOH = 14.00 – 1.44 = 12.56
Acid-Base Indicators
 Weak acids that undergo a colour change as the pH
changes
Percentage Ionization
 Not all acids (or bases) undergo complete ionization or
dissociation.
 Acids and bases that partially ionize are called "weak"
acids or bases
 e.g. Acetic Acid, HC2H3O2 is a weak acid
 Ammonia, NH3, is a weak base
Read pgs 454-462
Do # 6, 7, 10, 15, 16 on page 463
References
 Rafa Muñoa
 W Sautter
 McGraw Hill Ryerson 11
 Nelson, Chemistry 11