Properties of Acids
Have a sour taste. Vinegar owes its taste to acetic acid. Citrus
fruits contain citric acid.
Cause color changes in plant dyes.
React with certain metals to produce hydrogen gas.
2HCl (aq) + Mg (s)
MgCl2 (aq) + H2 (g)
React with carbonates and bicarbonates
to produce carbon dioxide gas
2HCl (aq) + CaCO3 (s)
CaCl2 (aq) + CO2 (g) + H2O (l)
Aqueous acid solutions conduct electricity.
1
Properties of Bases
Have a bitter taste.
Feel slippery. Many soaps contain bases.
Cause color changes in plant dyes.
Aqueous base solutions conduct electricity.
Examples:
2
Arrhenius acid is a substance that produces H+ (H3O+) in water
Arrhenius base is a substance that produces OH- in water
3
Hydronium ion, hydrated proton, H3O+
4
A Brønsted acid is a proton donor
A Brønsted base is a proton acceptor
base
acid
acid
base
A Brønsted acid must contain at least one ionizable
proton!
5
Monoprotic acids
HCl
H+ + Cl-
HNO3
CH3COOH
Strong electrolyte, strong acid
H+ + NO3H+ + CH3COO-
Strong electrolyte, strong acid
Weak electrolyte, weak acid
Diprotic acids
H2SO4
H+ + HSO4-
Strong electrolyte, strong acid
HSO4-
H+ + SO42-
Weak electrolyte, weak acid
Triprotic acids
H3PO4
H+ + H2PO4-
Weak electrolyte, weak acid
H2PO4-
H+ + HPO42-
Weak electrolyte, weak acid
HPO42-
H+ + PO43-
Weak electrolyte, weak acid
6
7
Identify each of the following species as a Brønsted acid, base, or both. (a) HI, (b)
CH3COO-, (c) H2PO4-
HI (aq)
H+ (aq) + I- (aq)
CH3COO- (aq) + H+ (aq)
H2PO4- (aq)
H2PO4- (aq) + H+ (aq)
Brønsted acid
CH3COOH (aq)
H+ (aq) + HPO42- (aq)
H3PO4 (aq)
Brønsted base
Brønsted acid
Brønsted base
8
Neutralization Reaction
acid + base
HCl (aq) + NaOH (aq)
H+ + Cl- + Na+ + OH-
H+ + OH-
salt + water
NaCl (aq) + H2O
Na+ + Cl- + H2O
H2O
9
Neutralization Reaction Involving a Weak
Electrolyte
weak acid + base
HCN (aq) + NaOH (aq)
HCN + Na+ + OH-
HCN + OH-
salt + water
NaCN (aq) + H2O
Na+ + CN- + H2O
CN- + H2O
10
Neutralization Reaction Producing a Gas
acid + base
2HCl (aq) + Na2CO3 (aq)
2H+ + 2Cl- + 2Na+ + CO32-
2H+ + CO32-
salt + water + CO2
2NaCl (aq) + H2O +CO2
2Na+ + 2Cl- + H2O + CO2
H2O + CO2
11
Sample Problem 4.4
PROBLEM:
Writing Ionic Equations for Acid-Base Reactions
Write balanced molecular, total ionic, and net ionic equations for each of
the following acid-base reactions and identify the spectator ions.
(a) strontium hydroxide(aq) + perchloric acid(aq)
(b) barium hydroxide(aq) + sulfuric acid(aq)
PLAN:
SOLUTION:
reactants are strong acids and
bases and therefore completely
ionized in water
(a) Sr(OH)2(aq)+2HClO4(aq)
products are
water
spectator ions
2H2O(l)+Sr(ClO4)2(aq)
Sr2+(aq) + 2OH-(aq)+ 2H+(aq)+ 2ClO4-(aq)
2H2O(l)+Sr2+(aq)+2ClO4-(aq)
2OH-(aq)+ 2H+(aq)
2H2O(l)
(b) Ba(OH)2(aq) + H2SO4(aq)
2H2O(l) + BaSO4(aq)
Ba2+(aq) + 2OH-(aq)+ 2H+(aq)+ SO42-(aq)
2H2O(l)+Ba2+(aq)+SO42-(aq)
2OH-(aq)+ 2H+(aq)
2H2O(l)
Figure 4.7
Start of titration
Excess of acid
An acid-base titration.
Point of
neutralization
Slight excess of
base
Sample Problem 4.5
PROBLEM:
Titration
You perform an acid-base titration to standardize an HCl solution by
placing 50.00 mL of HCl in a flask with a few drops of indicator solution.
You put 0.1524 M NaOH into the buret, and the initial reading is 0.55 mL.
At the end point, the buret reading is 33.87 mL. What is the
concentration of the HCl solution?
PLAN:
volume(L) of base
multiply by M of base
mol of base
molar ratio
mol of acid
divide by L of acid
M of acid
Finding the Concentration of Acid from an Acid-Base
SOLUTION:
NaOH(aq) + HCl(aq)
(33.87-0.55) mL x
NaCl(aq) + H2O(l)
1L
= 0.03332 L
103 mL
0.03332 L
X 0.1524 M
= 5.078x10-3 mol
NaOH
Molar ratio is 1:1
5.078x10-3 mol HCl
0.05000 L
= 0.1016 M HCl
Figure 4.8
An aqueous strong acid-strong base reaction on the atomic scale.