Chemistry 114
Second Hour Exam
Name:____________
(4 points)
Please show all work for partial credit
1. ( 12 points) Use the phase diagram for helium (below) to answer the following questions:
Note that He I and He II are two different liquid
forms of helium.
A. At what temperature and pressure is the critical point for helium?
B. List the temperature and pressure for all triple points for helium.
C. Does Helium have a normal melting point, if so what is the value of the normal
melting point.
D. Does Helium have a normal boiling point, if so what is the value of the normal
boiling point.
E. What is the form of Helium at 3 K and 10 kPa?
F. What is the form of Helium at 1K and 8,000 kPa?
2. Lithium crystalizes in a face centered cubic lattice and has a density of .535g/cm3.
A. (8 points) What is the volume of the lithium unit cell.
B. (4 points) What is the length of an edge of a lithium unit cell?
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3. A saturated solution of NaCl contains 36 g or NaCl for every 100 g of water, and has a
density of 1.197 g/ml.
A. (2 points) What is the molality (m) of NaCl in this solution?
B. (1 point) What is the colligative molality (mc) of NaCl in this solution?
C. (3 points) What is the mole fraction (÷) of NaCl in this solution?
D. (3 points) What is the molarity (M) of NaCl in this solution?
E. (3 points) What is the weight % of NaCl in this solution?
4. Benzene has a normal freezing point of 5.49oC and a freezing point depression constant
Kf of 5.12 oC/m. It also has a normal boiling point of 80.1oC, and Boiling point elevation
constant of 2.53 oC/m.
A. (6 points) If I have a solution of benzene that has a freezing point of 1.0oC, what
it the colligative molality of that solution?
B. (6 points) What is the boiling point of the above solution?
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5. I have an aqueous solution of Aluminum chloride that has an osmotic pressure of 10 atm
at 25oC.
A. (6 points) What is the colligative molarity of this solution.
B. (3 points) What is the molar concentration of aluminum ion in this solution?
C. (3 points) What is the molar concentration of chloride ion in this solution.
6. Define the following terms:
Unit cell
Metallic-covalent bond
solute
van’t Hoff factor
k in the equation: rate=k[A]b
b in the equation: rate=k[A]b
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7. I have gathered the following data in a series of three initial rate experiments for the
reaction of 2A + 3B 62C.
[A] (M)
0.7
1
1
[B] (M)
0.7
0.7
1.4
rate (M/s)
6.89
20.1
33.8
A. (3 points) Write the rate law equation for this reaction.
B. (3 points) Determine the order parameter for A in this reaction.
C. (3 points) Determine the order parameter for B in this reaction.
D. (3 points) Determine the rate constant for this reaction.
8. (12 points) If the initial concentration of a reactant is .05 M in a second order
reaction with a rate constant of .02 M-1sec-1, how long will it be before the concentration
of the reactant has dropped to .0125 M?
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