Chemistry Chapter 15
Acids and Bases
Acids
and
Bases
Some Definitions
• Arrhenius acids and bases
Acid: Substance that, when dissolved in
water, increases the concentration of
hydrogen/hydronium ions (protons, H+ or
H3O+).
Base: Substance that, when dissolved in
water, increases the concentration of
hydroxide ions.
Acids
and
Bases
Some Definitions
• Brønsted–Lowry: must have both
1. an Acid: Proton donor
and
2. a Base:
Proton acceptor
Acids
and
Bases
Brønsted-Lowry acids and bases are always paired.
The Brønsted-Lowry acid donates a proton,
while the Brønsted-Lowry base accepts it.
Which is the acid and which is the base in each of these rxns?
Acids
and
Bases
What Happens When an Acid
Dissolves in Water?
• Water acts as a
Brønsted–Lowry base
and abstracts a proton
(H+) from the acid.
• As a result, a
hydronium ion (H3O+)
is formed.
Acids
and
Bases
Ionization of HCl and formation of
hydronium ion, H3O+
H2 O +
Proton
acceptor
HCl

H3O+ + Cl-
Proton
donor
Acids
and
Bases
A Brønsted–Lowry acid…
…must have a removable (acidic) proton.
HCl, H2O, H2SO4
A Brønsted–Lowry base…
…must have a pair of nonbonding electrons.
NH3, H2O
Acids
and
Bases
Salts
• Compounds that dissociate releasing
neither H+ or OH- ions
• Example:
KCl  K+ + Cl-
Acids
and
Bases
Properties of Acids
 Acids taste sour
 Acids affect indicators
 Blue litmus turns red
 Methyl orange turns red
 Acids have a pH lower than 7
 Acids are proton (hydrogen ion, H+) donors
 Acids react with active metals, produce H2
 Acids are electrolytes
 Acids neutralize bases to produce a salt
and water
Acids
and
Bases
Acids change Indicators
Blue litmus paper turns red in contact
with an acid.
Acids
and
Bases
Acids React with Active
Metals
Acids react with active metals to form
salts and hydrogen gas.
Mg + 2HCl  MgCl2 + H2(g)
Acids
and
Bases
Acids Neutralize Bases
HCl + NaOH  NaCl + H2O
Neutralization reactions ALWAYS
produce a salt and water.
Acids
and
Bases
Acids are Proton Donors
Monoprotic acids
Diprotic acids
HCl
H2SO4
HC2H3O2
H2CO3
Triprotic acids
H3PO4
HNO3
Acids
and
Bases
Uses
• H3PO4 - soft drinks, fertilizer, detergents
• H2SO4 - fertilizer, car batteries
• HCl - gastric juice
• HC2H3O2 - vinegar
Acids
and
Bases
Acids you must know:
Strong Acids
Weak Acids
Sulfuric acid, H2SO4
Phosphoric acid, H3PO4
Hydrochloric acid, HCl
Acetic acid, HC2H3O2
Nitric acid, HNO3
Hydrobromic acid, HBr
Hydroiodic acid, HI
Perchloric acid, HClO4
Acids
and
Bases
Properties of Bases
 Bases taste bitter
 Bases affect indicators
 Red litmus turns blue
 Phenolphthalein turns purple
 Bases have a pH greater than 7
 Bases are proton (hydrogen ion, H+) acceptors
 Solutions of bases feel slippery
 Bases neutralize acids to produce a salt and
water
Acids
and
Bases
Examples of Bases




Sodium hydroxide (lye), NaOH
Potassium hydroxide, KOH
Magnesium hydroxide, Mg(OH)2
Calcium hydroxide (lime), Ca(OH)2
Acids
and
Bases
Uses
• NaOH - lye, drain and oven cleaner
• Mg(OH)2 - laxative, antacid
• NH3 - cleaners, fertilizer
Acids
and
Bases
Naming Acids, Bases, Salts
• Bases & Salts- Ionic
Name the same as ionic compounds
• Acids
Binary
• 2 elements, first hydrogen
• Hydro___ic acid
Ternary
• 3 elements, change ending
• -ate  ic, -ite  ous
Acids
and
Bases
Strong Acids vs. Weak Acids
Strong acids are assumed to be 100%
ionized in solution (good proton donors).
HCl
H2SO4
HNO3
Weak acids are usually less than 5%
ionized in solution (poor proton donors).
H3PO4
HC2H3O2
Organic acids
Acids
and
Bases
Strong Acid Dissociation
Acids
and
Bases
Weak Acid Dissociation
Acids
and
Bases
Concept Test
• Which of the following "molecular" pictures
best represents a concentrated solution of
the weak acid HA?
A
B
Acids
and
Bases
pH Scale
• pH
a measure of the concentration of H3O+ ions in
solution
measured with a pH meter or an indicator with
a wide color range
14
0
7
INCREASING
ACIDITY
NEUTRAL
INCREASING
BASICITY
Acids
and
Bases
Acids
Have a
pH less
than 7
Acids
and
Bases
Bases
have a pH
greater
than 7
Acids
and
Bases
pH Scale
pH of Common Substances
Acids
and
Bases
Neutralization Reaction
ACID + BASE  SALT + WATER
HCl + NaOH  NaCl + H2O
=
Acids
and
Bases
Neutralization does not always mean pH =
Neutralization Reaction
KOH + HNO3  H2O + KNO3
Acid?
HNO3
Base?
KOH
Salt?
KNO3
Acids
and
Bases
Products of Neutralization
HCl + NaOH 
NaCl + H2O
H2SO4 + Ca(OH)2  CaSO4 + 2 H2O
HNO3 + KOH  KNO3 + H2O
The products of neutralization are always
salt and _______.
water
a ______
Acids
and
Bases