Chapter 4
Part 2
CHM 108
SUROVIEC
SPRING 2014
I. Solution Stoichiometry
 According to the following reaction, how many moles of
Fe(OH)2 can form from 175.0 mL of 0.227 M LiOH
solution? Assume that there is excess FeCl2.
FeCl2(aq) + 2 LiOH(aq) → Fe(OH)2(s) + 2 LiCl(aq)
 Determine the number of grams H2 formed when 250.0
mL of 0.743 M HCl solution reacts with 3.41 x 1023 atoms
of Fe according to the following reaction.
2 HCl(aq) + Fe(s) → H2(g) + FeCl2(aq)
II. Aqueous Solution and Solubility
 Consider salt dissolving in water and sugar
dissolving in water.
A. Electrolyte
 The way ionic compounds vs. molecular compounds
dissolve in water shows the difference between types
of solution.
A. Electrolyte
 Electrolytes – ions that act at charge carriers
 Solutes that completely dissociate into ions are called
strong electrolytes
B. Solubility of Ionic Compounds
 Most ionic compounds when dissolved in water the
solute breaks into ions.
 Not true for all ionic compounds
Determine the insoluble compounds
 AgCl
 NaNO3
 PbCl2
 Ba(OH)2
III. Precipitation Reactions
Precipitate: insoluble solid that separates from
solution where no solid existed before reaction
 Hard water contains Ca2+ and Mg2+
 Laundry detergent contains Na2CO3

Examples
1.
silver nitrate and potassium chloride
2.
lead (II) nitrate and potassium chromate
potassium chromate and silver nitrate
sodium carbonate and copper (II) chloride
nickel (II) chloride and potassium hydroxide
3.
4.
5.
IV. Molecular and Ionic Equations
A. Molecular Equations
 Consider the following equation:
CaCl2 (aq) + Na2SO4 (aq)  CaSO4 (s) + 2NaCl (aq)
B. Ionic Equations
 In these equations, see that some of the ions are
present on both sides of the arrow
Example
Given:
2AgNO3(aq) + MgCl2(aq)  2AgCl (s) + Mg(NO3)2
(aq)
What is the ionic equation? Net Ionic?
Write NET ionic equations
1.
2.
AlCl3 (aq) + Na3PO4 (aq)
lead (II) nitrate and potassium chloride
IV. Acid and Base Reactions
 Bronstead definition of acid: proton donor
 Bronstead definition of base: proton acceptor
A.Acids
HCl (aq) + H2O (l) → H3O+ (aq) + Cl- (aq)
H2SO4 (aq)
HSO4- (aq)
H+ (aq) + HSO4- (aq)
H+ (aq) + SO42- (aq)
B. Bases
 Proton acceptors
 Strong bases ionize completely to OH NaOH (s) →
 Ca(OH)2 →
 Weak bases ionize only partially
 NH3 (aq) + H2O ⇌
C. Reactions of Acids and Bases
1.
Neutralization
acid + base
HCl (aq) + NaOH (aq)
salt + water
C. Reactions of Acids and Bases
2. Weak Acid/Base reactions
CH3COOH + NaOH
V. pH
 Concentration scale for acids and bases
Vinegar:
Pure Water:
Ammonia:
[H+] = 1.610-3M
[H+] = 1.010-7M
[H+] = 1.010-11M
pH = -log[H+]
Determine the pH of the above. What is the
trend of acids and bases?
VI. Acid-Base Titrations
 Commonly used to
determine the
concentration of a
dissolved species or its
percentage in a mixture
 Titration

Measuring the volume of a
standard solution (known
concentration) needed to
react with a measured
quantity of a sample
 Titrant (in the buret)
 Analyte (in the
Erlenmeyer flask)
VI. Acid-Base Titrations


Equivalence point is where the number of moles of acid equals
the number of moles of base
The endpoint is indicated by a color change in the acid-base
indicator
Example
1.
2.
What volume (in mL) of a 1.420 M NaOH solution
is required to titrate 25.00 mL of a 4.50 M H2SO4
solution?
What volume (in mL) of 0.955 M HCl is required
to titrate 2.152g of Na2CO3 to the equivalence
point?
VI. Redox Reactions
A. Oxidation Numbers


Needed when we are looking at reactions between 2
nonmetals.
The oxidation number of an atom in a compound is
the “charge” that it would have it all shared
electrons were assigned to the atom with higher
electronegativity.
III. Oxidation-Reduction Reactions
 Short name: Redox reactions
 Electron exchange
 Oxidation is a loss of electrons
 Reduction is a gain of electrons
III. Redox Reactions
Fe (s)  Fe? (aq) + 2e-
2H? (aq)+ 2e-  H2 (g)
Examples
A. Fe3+ (aq) + H2 (g)
B. Au (s) + F2 (aq)
1.
2.
3.
Fe2+ (aq) + H+ (aq)
F- (aq) + Au3+(aq)
Break into 1/2 reactions
Mass balance 1/2 reactions
Combine and check for neutrality and check again for mass
balance