Last Class
17.1 Acids, Bases, and the equilibrium concept
What is an acid?
17.1 Acids, Bases, and the equilibrium concept
17.2 Brønsted-Lowry definition of acids & bases
17.3 Water and the pH scale
17.2 Brønsted-Lowry acids & bases
17.3 Water and the pH scale
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What are the hydroxide and hydronium ion
concentrations in a 0.0012 M solution of NaOH at 25 oC?
What is pH?
Arnold Beckman – Inventor
of the pH Meter
pH
H = -log[H
l [H3O+]
pOH = -log[OH-]
The pH scale
Today
• 17.4 Equilibrium constants for Acids and Bases
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We need to know:
Neutral pH at different temperatures
Acid ionization constant
• Kw = 1.01 10-14 at 25 oC, neutral pH = 7.0
Base ionization constant
• Kw increases when T increase
T > 25 oC, neutral pH < 7.0
Water auto-ionization constant
T < 25 oC, neutral pH > 7.0
Recommended:
Simulation 17.3a
17.4
Common Acids and Bases
How can we define the strengths
of acids and bases?
Strong acid
Weak acid
Lower the pH Æ the stronger the acid
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What does it happen when we add to water:
Relative strength of an acid and a base
• HA (aq) + H2O (l) ' H3O+ (aq) + A- (aq)
Acid
Ka =
Base
• B (aq) + H2O (l) ' BH+ (aq) + OH- (aq)
Kb =
Salt
List of strong acid and bases: page 810 Kotz
17.4
Inccreasing Base Strength
In
ncreasing Acid Strength
h
Ionization of Acetic Acid,
A weak acid
KA = 1.8 x 10-5
17.4
Identifying the ionizable proton
17.4
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