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Chemistry 118 Exam Study Guide
1. Quantum-Mechanical Model of the Atom
Key Concepts :
o Electromagnetic radiation and atomic spectra
o Bohr model and quantum numbers (n , l ,m
l
, m
s
o Orbital shapes and electron configurations
Example Problem :
Q : What is the electron configuration for an atom of sulfur (S)?
A : Sulfur has 16 electrons, so the configuration is 1 s
2
2 s
2
2 p
6
3 s
2
3 p
4
2. Periodic Properties of Elements
Key Concepts :
o Atomic radius, ionization energy, and electronegativity trends
o How electron configurations affect element properties
Example Problem :
Q : Arrange the following elements in order of increasing atomic radius:
Na, Al, P, Cl.
A : Cl < P < Al < Na.
3. Molecules and Compounds
Key Concepts :
o Ionic and covalent compounds
o Naming compounds and writing formulas
o Molar mass and percent composition
Example Problem :
Q : What is the molar mass of
CaCl
2
A :
CaCl
2
: 40.08+ 2 ×35.45=110.98 g /mol .
4. Chemical Bonding 1: Lewis Structures and Molecular Shapes
Key Concepts :
o Lewis dot structures and formal charges
o VSEPR theory for predicting molecular shapes
Example Problem :
Q : Draw the Lewis structure for
NH
3
and determine its shape and bond
angles.
A : Shape: Trigonal pyramidal; Bond angle: ~107°.
5. Chemical Reactions and Chemical Quantities
Key Concepts :
o Balancing chemical equations
o Mole-to-mole relationships, limiting reactants, and percent yield
Example Problem :
Q : How many grams of
H
2
O
are produced from 5 grams of
2 H
2
+O
2
→ 2 H
2
O
A :
Molar mass H
2
= 2 g /mol ; Molar mass H
2
O= 18 g /mol
5 g H
2
×
1 mol H
2
2 g
×
2 mol H
2
O
2 mol H
2
× 18 g H
2
O= 45 g H
2
O
6. Solutions and Aqueous Reactions
Key Concepts :
o Solubility rules, concentration (Molarity), and types of reactions
in solution (precipitation, acid-base, redox)
Example Problem :
Q : How many moles of NaCl are in 500 mL of a 1.5 M NaCl solution?
A : Moles of NaCl=1.5 M × 0.5 L=0.75 mol.
rate and doubling [B] doubles the rate.
A :
Rate=k [ A]
2
[B]
11. Chemical Equilibrium
Key Concepts :
o The equilibrium constant (K) and Le Chatelier’s principle
Example Problem :
Q : For
N
2
+ 3 H
2
↔ 2 NH
3
, if
[NH
3
]=0.1 ,[N
2
]=0.5 ,[ H
2
]=1.
, calculate
K
c
A : K
c
2
3
12. Acids and Bases
Key Concepts :
o pH, pOH, strength of acids/bases, titrations, buffers
Example Problem :
Q : What is the pH of a 0.001 M HCl solution?
A : pH =−log (0.001)= 3
13. Aqueous Ionic Equilibrium
Key Concepts :
o Common ion effect, buffer solutions, solubility product (
K
sp
Example Problem :
Q : What is the solubility of AgCl in water if K
sp
=1.8× 10
− 10
A : Let ¿ K
sp
=s
2
Solving, s=
1.8 × 10
− 10
=1.34 × 10
− 5
M
