Chapter 17. Acids and Bases. Acids, Bases, and Matter. Classification of Matter. Arrhenius Definition of Acids and Bases. Acids Acidus – Latin for sour Substances that, when added to water, produce hydrogen ions, H+ (protons), or hydronium ions, H 3 O +. Bases
Acids and Bases
Classification of Matter
H2O + H2O <---------> H3O+(aq) + OH-(aq)
HX(aq) + H2O(l) ----------> H3O+(aq) + X-(aq)
HX(aq) + H2O(l) <-------> H3O+(aq) + X-(aq)
HB(aq) + H2O(l) <-----> H3O+(aq) + B-(aq)
Molecular Weak Acids
HIn(aq) + H2O(l) -----> H3O+(aq) + In-(aq)
Anions containing an ionizable H atom
Zn(H2O)42+ + H2O(l) <------->
H3O+(aq) + Zn(H2O)3OH+
Concentrations are governed by equilibrium constants - Kb.
B-(aq) + H2O(l) <-------> HB(aq) + OH-(aq)
NH3(aq) + H2O(l) <-----> NH4+(aq) + OH-(aq)
Anions derived from weak acids (conjugate bases):
F-(aq) + H2O(l) <------> HF(aq) + OH-(aq)
Pure Water [H3O+]= [OH-] = 1.00 x 10-7
Acidic [H3O+] > [OH-]
[H3O+] > 1.00 x10-7
Basic [H3O+] < [OH-]
[H3O+] < 1.00 x10-7
The hydronium ion concentration of an acidic solution was 1.00x105 M. What was the [OH]?
What is the hydronium ion concentration if the hydroxide concentration was 2.50x103 M?
Neutral: pH = 7.00
Acidic: pH < 7.00
Basic: pH > 7.00
pH paper is used that has compounds in it which are change to different colors for different pH ranges.
HIn(aq) + H2O(l) H3O+(aq) + In(aq).
E.g. phenolphthalein is colorless in acid form but pink in basic form.
Determine the pH of a solution in which [H3O+] = 5.40x106 M
Determine the pH of a solution in which the [OH] = 3.33x103 M
Determine the pOH of a solution in which the [OH] = 3.33x103 M
Determine the [H3O+] if the pH of the solution is 7.35.
Ka x Kb = [H3O+] [B-] / [HB] x [HB] [OH-] / [B-]
= [H3O+] [OH-] = 1.00x 10-14 = Kw
Calculating Ka or Kb from Initial Concentrations and Measured pH
Calculation of Ka (in water)
[H3O+] = [B-] = antilog –pH
Percent Ionization HB = [H3O+] / original concentration HB
Dissolving a weak acid, HB, in water
if x/a < 0.05 we take a - x = a
Calculating the pH of the Solution
(must have < octet or be positively charged)
(must have nonbonding electrons available for coordinate covalent bonding)