CHEM 1030 FORBES THIRD EXAM FINAL
REVIEW 2026 ACCURATE ANSWERS
GRADED A+
⩥ Intermolecular forces
are: Answer: attractive and repulsive forces which occur between two or
more molecules; greater force = molecules stick together more
⩥ Rank the following intermolecular forces in order of their strength
(least to greatest):
▪Dipole-ion forces
▪Dipole-induced dipole forces
▪London dispersion forces
▪Dipole-dipole forces. Answer: London dispersion forces; Dipole-
induced dipole forces; Dipole-dipole forces; Dipole-ion forces
⩥ Hydrogen bonding. Answer: a specific kind of dipole-dipole
interaction where hydrogen forms a bond with X, where X is an atom
with high electronegativity.
⩥ London Dispersion Forces (LDF). Answer: intermolecular forces
between atoms or non-polar molecules due to induced dipoles; Strength
of induced dipole depends on the polarizability of the atom/molecule.
,⩥ Polarizability. Answer: ease with which electron cloud can be
displaced
⩥ Rules for Balancing Equations. Answer: 1. Balance the atom which is
present in the least number of molecules (e.g. sulfur)
2. Balance the next atom based on the lowest number of molecules
3. Check to make sure the first atom is still balanced, if not, then
rebalance this atom
4. Continue this process until all atoms are balanced
⩥ Stoichiometry. Answer: Mathematical concept which relates the
amount of products to amount of reactants
⩥ Stoichiometry ratio is:. Answer: the ratio of molar coefficients for any
two molecules in a chemical reaction
⩥ percent composition. Answer: Ratio of the total mass of one element
to the total mass of the substance
⩥ Rules to Determine Chemical Formula From Percent Composition.
Answer: 1. Assume we have a 100 g sample of element X
2. Determine the mass of each element based on the percentage
3. Determine the moles of each element based on molar mass.
, 4. Determine the stoichiometric ratio of both elements. This will directly
give the empirical chemical formula of magnetite
⩥ Empirical formulas. Answer: represent the smallest stoichiometric
ratios between elements in a substance
⩥ Molecular formulas. Answer: give the exact number of atoms of each
element in a compound
⩥ Rules to determine empirical and molecular formulas. Answer: 1.
Determine empirical formula based on method for ionic compounds
1a. Convert % to mass based on 100 g sample
1b. Convert mass to moles based on molar mass
1c. Use mole ratio to determine empirical formula
2. Determine how many formula units are needed to equal measured
mass
3. Multiple this number by the empirical formula to achieve the
molecular formula
⩥ Combustion analysis. Answer: an experimental procedure which
determines that empirical formula of an unknown molecule based on
how much CO2 and H2O are produced
REVIEW 2026 ACCURATE ANSWERS
GRADED A+
⩥ Intermolecular forces
are: Answer: attractive and repulsive forces which occur between two or
more molecules; greater force = molecules stick together more
⩥ Rank the following intermolecular forces in order of their strength
(least to greatest):
▪Dipole-ion forces
▪Dipole-induced dipole forces
▪London dispersion forces
▪Dipole-dipole forces. Answer: London dispersion forces; Dipole-
induced dipole forces; Dipole-dipole forces; Dipole-ion forces
⩥ Hydrogen bonding. Answer: a specific kind of dipole-dipole
interaction where hydrogen forms a bond with X, where X is an atom
with high electronegativity.
⩥ London Dispersion Forces (LDF). Answer: intermolecular forces
between atoms or non-polar molecules due to induced dipoles; Strength
of induced dipole depends on the polarizability of the atom/molecule.
,⩥ Polarizability. Answer: ease with which electron cloud can be
displaced
⩥ Rules for Balancing Equations. Answer: 1. Balance the atom which is
present in the least number of molecules (e.g. sulfur)
2. Balance the next atom based on the lowest number of molecules
3. Check to make sure the first atom is still balanced, if not, then
rebalance this atom
4. Continue this process until all atoms are balanced
⩥ Stoichiometry. Answer: Mathematical concept which relates the
amount of products to amount of reactants
⩥ Stoichiometry ratio is:. Answer: the ratio of molar coefficients for any
two molecules in a chemical reaction
⩥ percent composition. Answer: Ratio of the total mass of one element
to the total mass of the substance
⩥ Rules to Determine Chemical Formula From Percent Composition.
Answer: 1. Assume we have a 100 g sample of element X
2. Determine the mass of each element based on the percentage
3. Determine the moles of each element based on molar mass.
, 4. Determine the stoichiometric ratio of both elements. This will directly
give the empirical chemical formula of magnetite
⩥ Empirical formulas. Answer: represent the smallest stoichiometric
ratios between elements in a substance
⩥ Molecular formulas. Answer: give the exact number of atoms of each
element in a compound
⩥ Rules to determine empirical and molecular formulas. Answer: 1.
Determine empirical formula based on method for ionic compounds
1a. Convert % to mass based on 100 g sample
1b. Convert mass to moles based on molar mass
1c. Use mole ratio to determine empirical formula
2. Determine how many formula units are needed to equal measured
mass
3. Multiple this number by the empirical formula to achieve the
molecular formula
⩥ Combustion analysis. Answer: an experimental procedure which
determines that empirical formula of an unknown molecule based on
how much CO2 and H2O are produced
