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Chapter 14
Acids and Bases
General Properties of Acids
1. An acid tastes sour - acidus = Latin, sour;
acetum= Latin, vinegar
2. An acid turns indicator dye litmus from blue to red.
3. An acid reacts with certain metals (Fe, Sn, Zn, Mg).
4. An acid is an electrolyte.
5. An acid reacts with bases to form salts and water
1. HNO2 is named
A)
B)
C)
D)
E)
hydronitric acid.
hydronitrous acid.
nitric acid.
nitrous acid.
hydrogen nitrite.
NO3- = nitrate
NO2- = nitrite
Common Acids
Name
Formula
Uses
Strength
Perchloric
HClO4
explosives, catalysts
Strong
Nitric
HNO3
explosives, fertilizers, dyes, glues
Strong
Sulfuric
H2SO4
Strong
Hydrochloric
HCl
Phosphoric
H3PO4
explosives, fertilizers, dyes, glue,
batteries
metal cleaning, food prep, ore
refining, stomach acid
fertilizers, plastics, food
preservation
Chloric
HClO3
explosives
Moderate
Acetic
HC2H3O2
plastics, food preservation,
vinegar
Weak
Hydrofluoric
HF
metal cleaning, glass etching
Weak
Carbonic
H2CO3
soda water, blood buffer
Weak
Hypochlorous
HClO
sanitizer
Weak
Boric
H3BO3
eye wash
Weak
Strong
Moderate
Sources of Acids
SO3
+
H2O
---------->
H2SO4
Sulfuric Acid
NO2
+
H2O
---------->
HNO3
Nitric Acid
CO2
+
H2O
---------->
H2CO3
Carbonic Acid
2 NaCl + H2SO4 ----------> Na2SO4 + 2 HCl Hydrochloric Acid
General Properties of Bases
1. A base tastes bitter
2. A base turns indicator dye litmus from red to blue.
3. A base feels slippery or soapy when mixed with a
small amount of water
4. A base reacts with acids to form salts and water
2. What is the chemical formula for the base
calcium hydroxide?
A)
B)
C)
D)
E)
CaOH
CaH
CaH2
Ca(OH)2
Ca2(OH)
Ca2+
OH-
Common Bases
Name
Formula
Common Name
Uses
Strength
Sodium
Hydroxide
NaOH
Lye, Caustic Soda
soap, plastic production,
petroleum refining
Strong
Potassium
Hydroxide
KOH
Caustic Potash
soap, cotton processing,
electroplating
Strong
Calcium
Hydroxide
Ca(OH)2
Slaked Lime
cement
Strong
Sodium
Bicarbonate
NaHCO3
Baking Soda
food preparation, antacids
Weak
Magnesium
Hydroxide
Mg(OH)2
Milk of Magnesia
antacids
Weak
Ammonium
Hydroxide
NH4OH
Ammonia Water
fertilizers, detergents,
explosives
Weak
Sources of Bases
CaO + H2O
---------->
Ca(OH)2 Calcium hydroxide
Li2O + H2O
---------->
2 LiOH
2 Na
Ca
+
+
2 H 2O
2 H 2O
Lithium hydroxide
----------> 2 NaOH + H2
Sodium hydroxide
---------->
Ca(OH)2
+
H2
Molecular Definitions
of
Acids and Bases
Acids and Bases in Solution
Acids “ionize” in water to form H+ ions.
(More precisely, the H+ from the acid molecule is donated
to a water molecule to form hydronium ion, H3O+)
Bases “dissociate” in water to form OH- ions.
(Bases, such as NH3, that do not contain OH- ions,
produce OH- by pulling H+ off water molecules.)
In the reaction of an acid with a base, the H+ from the acid
combines with the OH- from the base to make water.
The cation from the base combines with the anion from the
acid to make a salt.
acid + base ➜ salt + water
Arrhenius Theory
3. Which of the following can act as an
Arrhenius base?
A)
B)
C)
D)
E)
Ca(OH)2
H 2O
KOH
H2SO4
Two of the above
Brønsted-Lowry Theory
Brønsted-Lowry Acid-Base Reactions involve transfer
of protons.
A Brønsted-Lowry Acid is a proton donor.
A Brønsted-Lowry Base is a proton acceptor.
Brønsted-Lowry Theory
An acid-base reaction involves proton
transfer:
H-A + [B:]- ——-> A:- + H-B
[H-A] + B: ——-> [A:]- + [H-B]+
[H-A:]- + B: ——-> [:A:]2- + [H-B]+
[H-A]+ + B: ——-> A: + [H-B]+
Brønsted-Lowry Acids
A Brønsted-Lowry Acid is a proton donor.
Any material with a H is a potential proton
donor, but because of molecular structure,
one or more protons are sometimes more
likely to be transferred.
Molecular Models of Selected Acids
4. Which of the following can act as a Brønsted–Lowry acid?
A)
B)
C)
D)
E)
NH3
NaOH
BF3
HBr
Two of the above
Ionization of an Acid
The ionization of an acid in water is more accurately written as:
HCl
+
H2O
---------->
Cl-
+
-
proton
donor
proton
acceptor
[H3O]+
+
chloride hydronium
ion
ion
Ionization of an Acid
Brønsted-Lowry Bases
A Brønsted-Lowry Base is a proton acceptor.
Any material with a lone pair of electrons is
a potential proton acceptor, but because of
molecular structure, one or more atoms with
lone pairs may be more likely to accept a
proton.
Bronsted Lowry Acid Base Reaction
Conjugate Pairs
1. In a Brønsted-Lowry reaction, the original base
becomes an acid in the reverse reaction, and the
original acid becomes a base in the reverse process
2. Each reactant and product are a conjugate pair.
3. The original base becomes a conjugate acid, and
the original acid becomes a conjugate base
Conjugate Acid Base Pairs
H-A
acid
+ :B
base
HCHO2 + H2O
acid
H2O
acid
base
+ NH3:
base
:A-
+
H-B+
conjugate
base
CHO2-
conjugate
acid
+
conjugate
base
HOconjugate
base
H3O+
conjugate
acid
+
NH4+
conjugate
acid
Conjugate Pairs
H2O and OH- are an
acid/base conjugate
pair.
NH3 and NH4+ are an
base/acid conjugate
pair.
5. Identify the two Brønsted–Lowry acids in the
following reaction:
H3PO4 + NH3 ⇄ NH4+ + H2PO4–
A)
B)
C)
D)
E)
H3PO4 and NH3
H3PO4 and NH4+
H3PO4 and H2PO4–
NH3 and NH4+
NH3 and H2PO4–
6. What is the conjugate acid of H2C6H5O6– ?
A)
B)
C)
D)
E)
C6H5O63–
HC6H5O62–
H2C6H5O6–
H3C6H5O6
H4C6H5O6+
Lewis Acids and Bases
electron pair donor = Lewis Base = nucleophile
electron pair acceptor = Lewis Acid = electrophile
Lewis acid-base reactions include all the
previously described acid-base reactions plus
additional types.
Molecules as Lewis Acids and Bases
The reaction of the Lewis acid BF3
with the Lewis base NH3
-+
Reactions
of
Acids and Bases
Acid-Base Reactions
Also called neutralization reactions because the
acid and base neutralize each other’s properties
2 HNO3(aq) + Ca(OH)2(aq) ➜ Ca(NO3)2(aq) + 2 H2O(l)
Note that the cation from the base combines with the
anion from the acid to make the water soluble salt.
The net ionic equation for an acid-base reaction is
H+(aq) + OH-(aq) ➜ H2O(l)
(as long as the salt that forms is soluble in water)
Neutralization - The reaction
of an acid and a base
HCl
+
NaOH ---------->
NaCl
+
H 2O
7. What is the salt formed in the neutralization reaction
between nitric acid and potassium hydroxide?
A)
B)
C)
D)
E)
KCl
KNO2
KNO3
H 2O
KH
HNO3 (aq) + KOH (aq)→ KNO3 (aq) + H2O (l)
Other Useful Acid-Base Reactions
1. Mg(OH)2
+
2 HCl
2. CaCO3
+
H2SO4
3. NaHCO3
+
RCOOH
----------> 4 H2O
---------->
---------->
+
H2O + CO2
MgCl2
+ CaSO4
H2O + CO2 +
RCOO-Na+
Titrations
A specific volume of the
solution to be titrated
is added to a flask.
An indicator is added.
A titrant (OF KNOWN
CONCENTRATION) is
added to the solution being
titrated until the indicator
changes colore.
The volume of titrant added
from the buret is measured.
THE CONCENTRATION OF
THE ORIGINAL SOLUTION
IS THEN DETERMINED BY
CALCULATION.
8. A 25.0 mL solution of 3.00 M hydrochloric acid requires
65.6 mL of NaOH solution to reach the endpoint. Calculate
the original concentration of the NaOH.
A)
B)
C)
D)
E)
1.14 M
0.381 M
0.257 M
3.00 M
3.43 M
HCl (aq) + NaOH (aq)→ NaCl (aq) + H2O (l)
How many moles of HCl reacted?
How many moles of NaOH reacted?
In what volume was the NaOH contained?
What is the molarity of the NaOH solution?
3.00 mol HCl
1.00 mol NaOH
0.0250 L HCl solution X
X
1.00 L HCl solution
1.00 mol HCl
= 0.0750 mol NaOH
M = mol/L =
0.0750 mol NaOH
0.0656 L NaOH solution
= 1.14 M NaOH
9. A 25.0 mL solution of 3.00 M phosphoric acid requires
65.6 mL of NaOH solution to reach the endpoint. Calculate
the original concentration of the NaOH.
A)
B)
C)
D)
E)
1.14 M
0.381 M
0.257 M
3.00 M
3.43 M
H3PO4 (aq) + 3 NaOH (aq)→ Na3PO4 (aq) + 3 H2O (l)
How many moles of H3PO4 reacted? How many moles of NaOH reacted?
In what volume was the NaOH contained?
What is the molarity of the NaOH solution? ✔
3.00 mol H3PO4
3.00 mol NaOH
0.0250 L H3PO4 solution X 1.00 L H3PO4 solution X
1.00 mol H3PO4
= 0.225 mol NaOH
M = mol/L =
0.225 mol NaOH
0.0656 L NaOH solution
= 3.43 M NaOH
Why not use M1V1 = M2V2 for titrations ??
HCl (aq) + NaOH (aq)→ NaCl (aq) + H2O (l)
3.00 mol HCl
1.00 mol NaOH
0.0250 L HCl solution X
X
1.00 L HCl solution
1.00 mol HCl
= 0.0750 mol NaOH
H3PO4 (aq) + 3 NaOH (aq)→ Na3PO4 (aq) + 3 H2O (l)
3.00 mol H3PO4
3.00 mol NaOH
0.0250 L H3PO4 solution X 1.00 L H3PO4 solution X
1.00 mol H3PO4
= 0.225 mol NaOH
10. What volume of a 0.4590 M NaOH solution is required to
reach the endpoint in the titration of 25.00 mL sample of 0.3669
M H2SO4?
H2SO4 (aq) + 2 NaOH (aq)→ Na2SO4 (aq) + 2 H2O (l)
A)
B)
C)
D)
E)
39.97 mL
31.28 mL
How many moles of H2SO4 reacted?
26.66 mL
How many moles of NaOH reacted?
19.98 mL
25.00 mL What volume of NaOH was needed?
0.3669 mol H2SO4
0.02500 L H2SO4 solution X
1.00 L H2SO4 solution
X
2.00 mol NaOH
1.00 mol H2SO4
= 0.01834 mol NaOH
1.00 L NaOH solution
0.01834 mol NaOH X
= 0.03997 L NaOH solution
0.4590 mol NaOH
2 NaOH (aq) + H2SO4 (aq)
→ Na2SO4 (aq) + 2 H2O (l)
L solution A
L solution B
M
M
mol compound B
mol compound A
mol/mol
ratio
The Big Picture of Stoichiometry
Liters of a
Solution of A
Molarity
Grams of
A
Grams of
B
Molar Mass
Molar Mass
Moles of
A
Moles of
B
Avogadro’s Number
Avogadro’s Number
Particles of
A
Particles of
B
Coefficients
Molarity
Liters of a
Solution of B