Chemistry
Test 3 Study Guide
Chemical Bonding:
Ionic Bonds:





Transfer electrons
Cation is a metal, anion is a non-metal/metalloid
Write formula to balance + and – charges (including polyatomic ions)
Change anion ending to –ide for binary compounds
Electronegativity differences greater than 1.67
Covalent Bonds:




Share electrons
Use prefixes to indicate number of each element involved
Electronegativity differences less than 1.67
o Between 0 – 0.5 is pure covalent (non-polar)
o Between 0.5 – 1.67 is polar covalent (polar)
Diatomic molecules “hunkle brif”: H2, O2, N2, Cl2, Br2, I2, F2
Lewis Dot Structures:
1) Count valence electrons
2) Give each element an octet (8), except for H which gets a pair (2)
VSEPR – Valence Shell Electron Pair Repulsion
Bonded Regions Lone Pairs
Shape
1 or 2
0
Linear
2
1 or 2
Bent
3
0
Trigonal planar
3
1
Trigonal pyramidal
4
0
Tetrahedral
Intermolecular Forces:



Van der Waals – weakest, between non-polar molecules
Dipole-Dipole – between polar molecules
H-Bonds – between molecules with H and either N, F or O
o Accounts for water’s expansion as it freezes and its surface tension
Law of Definite Proportions
Law of Multiple Proportions
Amounts:


Avogadro’s Number (AN) = 6.02 x 1023 particles (or atoms or molecules) = 1 mole
Molar Mass = sum of atomic masses in grams = 1 mole
Empirical Formula
Hydrate Lab
Vocab to know: anion, binary compound, cation, empirical formula, hydrate, molar mass, mole,
molecular formula, monatomic ion (ex. K1+), polyatomic ion (ex. NO31-),
Practice Problems:
1) Find the molar mass of Al2S3.
2) What is the mass in grams of 2.50 moles of oxygen gas?
3) How many moles of compound are in 77.1g Cl2?
4) How many molecules are in 77.1 g Cl2?
5) What is the percent composition of PbCl2?
6) What is the empirical formula for C6H12O6?
7) What is the empirical formula for a compound that contains 32.38% sodium, 22.65% sulfur and
44.99% oxygen?
a) If you had a 100 gram sample of the compound, how many grams of each element would you
have?
b) How many moles of each element would that be?
c) Find the smallest whole-number mole ratios.
d) Write the empirical formula of the compound.
8) What is the molecular formula of a compound whose empirical formula is P2O5 and whose molar
mass is 283.89 g/mol?
9) List the prefixes for 1-10. (ex. 1 = mono)
10) List the 7 diatomic molecules.