Name
Directions: Show all work. Show all units. Show all lone pair. Show all formal charges.
1. The strongest intermolecular forces present in an ensemble of CH3COCF3 molecules are: (2)
a.) hydrogen bonding forces
b.) dipole-dipole forces
c.) London dispersion forces
d.) ion-dipole forces
2. Which of the following statements about gases is true? (2)
a.) The ideal gas law is invalid at low volumes
b.) No gas is actually “ideal”
c.) A sample of gas consists of tightly packed molecules in constant motion, according to kinetic theory
d.) Volume and temperature are inversely proportional at constant pressure
3. A certain gas is trapped inside of a sealed container at volume V1 and temperature T1. If the temperature
of the gas is tripled at constant pressure, what is V2 in terms of V1? (2)
1
a.) V2 = 3(V1)
b.) V2 =3 (V1)
c.) V2 = (V1)3
d.) not enough information to determine
4. Unlike most substances on earth, solid water (i.e. ice) has a lower density the liquid form. Why? (2)
a.) Repulsion of partial negative charges on oxygen atoms causes ice to expand, lowering its density.
b.) Ice molecules spread out to maximize hydrogen bonding interactions, lowering the density.
c.) Ice molecules clump together to maximize hydrogen bonding interactions, lowering the density.
d.) Repulsion of partial positive charges on hydrogen atoms causes ice to expand, lowering its density.
5. A cylindrical tube with two open ends is submerged in a certain liquid. The cohesion forces are much
stronger than the adhesive forces. Which of the following must be true: (2)
a.) The viscosity of the solution is high
b.) Capillary action draws the liquid up the tube
c.) The liquid has high surface tension
d.) Nothing happens
6. Arrange the following molecules in order of increasing boiling point. (7)
CH3CHNH, CH4, SF6, CH3OH, C(OH)4, H2O, PCl3
7. Explain London Dispersion forces. (6)
8a. Explain the difference between formal and partial charges. (3 ½)
8b. Why are hydrogen bonds so strong? (4 ½)
9. Explain atmospheric pressure. (4)
10. A student prepares a 0.50M solution of K3PO4 (aq) by adding a 95mL aliquot of a pre-made stock
solution to 155mL of water. What is the molarity (concentration) of the stock solution? (7)
11. Fill in the table below. Simply write the hybridization (ex. sp3) of the central atom in the box provided.
Lone pair and formal charges MUST be shown for credit. Molecules MUST be drawn according to VSEPR.
Molecule
Lewis Structure (4)
Shape around
central atom (1)
Hybridization
(1)
# of σ and π bonds
in molecule (1)
HN3
CH2CHNCHCH3
chlorate
KrOF3-
12. Consider the molecule HCN. Draw the Lewis structure. Sketch out the atomic orbitals of the elements,
and clearly illustrate their merger to form hybrid orbitals. Make sure that you indicate any energetic
difference between orbitals. Finally, sketch the overlapping orbitals of the atoms, and label all sigma and pi
bonds. You may use the back of this page (10).
13. In a sealed, expandable reactor, 11.73 g of Vanadium (I) carbonate is added to 437.0 mL of 0.300M
hydrochloric acid (aq). The reaction proceeds at 62oC under a constant pressure of 2.30 atmospheres,
producing vanadium (I) chloride (aq), water, and carbon dioxide gas. If the actual volume of the gas
product is 0.609L, what is the % yield of the reaction to three significant figures? (20)
BONUS:
1. Nitroglycerin, C3H5N3O9 (L), is a dense liquid (ρ = 1.60 g/mL) that decomposes violently to yield carbon
dioxide gas, nitrogen gas, oxygen gas, and steam. If 3.0 mL of nitroglycerin reacts in a sealed 2.0L container
at 212oC, calculate the total vapor pressure exerted on the container. (10)
Equations
PV = nRT where R = 0.0821 L atm/ (mol K)
P1V1 = P2V2
%yield =(actual/theoretical) x 100%
n = MV
V1/T1 = V2/T2