Chem 200 Exam 3 Review Problems Fall 2009
NOTE: These are just some of the problem types that may appear on Exam 3. Review your
quizzes, notes (especially packet problems) and homework also. The exam will cover material
from: Ch 8 (8.4 – 8.5), Ch 9 (9.1 – 9.3, 9.5), Ch 10 (all), Chp 11 (11.1 – 11.2), Chp 5 (5.1 – 5.6) and
Ch 12 (12.3 – 12.5 and the material in 12.2 on pages 445-447 titled:“The Effects of Temp and
Intermolecular Forces on VP” and “VP and BP”). That's a lot of material! (although some of the
chapters are short). Start studying yesterday. I will give you the rms speed equation, Graham's law of
effusion equation, the Clausius Clayperon eq and any constants. You need to know the other gas laws
(Combined, Ideal, Dalton's Partial Pressures).
1. Calculate the density of nitrogen gas at 37C and 760. mmHg in grams per liter.
2. A balloon contains 10. L of a gas at 24C and 101.5 kPa. Suppose the gas in the balloon is heated
to 35C. If the volume is now 12 L, what is the pressure of the gas?
3. What is the density of nitrogen gas (N2) at STP?
4. How many liters does 37 g of nitrogen gas occupy at 40.C and 787 mmHg ?
5. What is the molar mass of a gas if 1.0 g occupies 2.0 L at 25C and 1.2 atm?
6. The partial pressures of CH4, N2 , and O2 in a sample of gas were found to be 100., 450., and 200.
mmHg, respectively. What is the total pressure? Calculate the mole fraction of nitrogen in the mixture.
7. Given the following equation: ZnSO3(s) 
ZnO(s) + SO2 (g)
a) What is the volume of SO2(g) produced at STP when 150. grams of ZnSO3(s) are consumed?
b) How many liters of SO2(g) could be obtained at 40.ºC and 787 mmHg if 150. grams of ZnSO3(s)
are consumed?
For the molecules and ions given below:
a. Draw the Lewis structure.
b. Predict the geometry of the molecule and the approximate bond angle.
c. State which hybrid orbitals would be expected for the central atom.
8. NH3
9. SF6
10. NH4+
11. BH3
12. HNO2
Would you expect the following molecules to be polar (Yes or No) ?
13. NH3
14. SO2
15. C2H6
16. H2O
17. BH3
18. There are 5 bonds in the following molecule. Label the bonds as  or  bonds.
H-CC–H
What orbitals are overlapping on each atom to cause each of the bonds you just labeled?
19. Potassium superoxide reacts with carbon dioxide to give oxygen gas:
4KO2(s) + 2CO2(g)  2K2CO3(s) + 3O2(g)
You combine 16.0 g KO2 with the carbon dioxide in a 4.00L tank, in which the gas pressure (of CO2)
is 1.24 atm at 23.0C. What is the pressure of the oxygen formed if captured in a 2.50 L flask at
25.0C ? (BIG HINT: what's the limiting reactant?)
20. Draw the Lewis structure of NO3- giving all possible resonance forms.
21. What is the molar mass of a gas that effuses at 1/6 the rate of helium?
22. What is the root mean square speed of H2 molecules at 50.C ?
23. A sample of Kr gas escapes through a tiny hole is 14 sec. How long would it take an identical
sample of Ne gas to effuse under the same conditions of T and P? (hint: how are rate and time related?)
24. Describe, in any order, the postulates of the Kinetic Molecular Theory.
25. This is the structure of acetaminophen, found in Tylenol:
O
HO
N
H
C
CH3
a) Give the hybridization and geometry of each C and N in the molecule (the ring is a benzene ring and
represents 6 C's, with alternating double bonds and H's as needed for each C to have 4 bonds; the N
and O's have lone pairs)
b) Calculate the formal charge of each O and N in the structure.
26. The normal boiling points of some substances are given below. Explain why these BP's are
different:
diethylether (CH3CH2OCH2CH3) BP 34.5C (The chain structure is C-C-O-C-C with the H’s on the
Cs)
ethanol (CH3CH2OH) BP 78C (The OH group is bonded to the rightmost C)
ethylene glycol (CH2(OH)CH2(OH) ) BP 197.2C (each OH is bonded to a C by C-O-H bonding)
27. Which of the following molecules can form hydrogen bonds?
a. CH4
b. H2O
c. NH3
d. HI
e. DNA
f. H2
28. For the molecules above that do not form H-bonds, which type or intermolecular force
predominates?
29. Explain how intermolecular forces influence the properties of liquids. In your explanation,
describe at least 3 liquid properties.
30. What is vapor pressure, how is it related to intermolecular forces and the boiling point of a liquid?
31. What condition must be met for a liquid to boil? What is meant by "normal boiling point"?
32. What is surface tension? viscosity?
33. skip
34. For the NH3 molecule, use orbital diagrams to illustrate the hybrid orbitals on the N.
35. For the CH4 molecule, describe which orbitals are overlapping to form the four bonds.
36. What quantities are graphed on the x and y axis when using the Clausius – Clayperon equation?
What info can we get from the slope of the resulting line?
37. At 34.1°C, the vapor pressure of water is 40.1 torr. What is the vapor pressure at 85.5°C? Use
40.7 kJ/mol as the Hvap of water.
38. If a gas is collected “over water” what must you take into account when doing any calculations
involving the gas?
39. Give the ground state electron configuration of the following ions: Cl-, Sr2+, Zn2+, Fe2+
40. Which of the following are paramagnetic: aluminum, aluminum ion, magnesium, magnesium ion.
41. What is the definition of first ionization energy? Which would have the higher 1st IE, K or Li?
Why?
42. Which atom is larger, Na or P? Why?
43. Which atom is larger, Na or Rb? Why?
44. Which is larger Na or Na+? Why?
45. Complete the following reactions: a) K2O + H2O 
b) SO3 + H2O 
True or False:
1. A lone pair of electrons tends to increase bond angles on the central atom.
2. The density of ice is less than the density of water.
3. Hydrogen bonds are stronger than covalent bonds.
4. Liquids have lower densities than gases.
5. The atoms or molecules that make up a solid have no motion.
6. The ideal gas law can fail at high temperatures and low pressures.
7. It is possible for water to boil at room temperature (25C).
8. There is no rotation possible around a double bond.
9. London Dispersion forces occur between all molecules.
10. When the temperature of a gas is doubled at constant volume, the pressure doubles.
11. According to the KM theory, collisions between gas molecules are inelastic.
12. According to the KM theory, the volume of gas particles is small compared with the volume of the
volume of the container they occupy.