CHEM 1412 Sample Exam I (Ch. 12, 13): 25 questions, total 100 points.
Answers are in bold.
Multiple Choice: Please select one best answer.
Q1-2. Consider “like dissolves like” rule or the solubility rule
1. Which of the following pair are soluble to each other?
(A) CH3COCH3 and H2O
(B) CCl4 and NaCl
(D) C6H12O6 and CCl4
(E) C2H5OH and Br2
2. Which of the following pair are insoluble to each other?
(A) NaCl and H2O
(B) CH3COOH and C2H5OH
(D) CH3OCH3 and H2O
(E) CH3OH and CCl4
(C) C6H12O6 and C6H6
(C) CH3COOH and H2O
3. Which of the following action will increase the solubility of a gas in water?
(A) Increasing pressure
(B) Increasing temperature
(C) Decreasing the molar mass
(D) Decreasing the polarity
4. What is the molarity of a solution made by dissolving 58.45 g NaCl in enough water to give
1000 mL of solution?
(A) 0.5 M
(B) 1.0 M
(C) 1.5 M
(D) 2.0 M
(E) 2.5 M
5 A 1.00 M Ba(OH)2 solution has a density of 1.50 g/mL. Calculate the molality (m) of Ba(OH)2.
(A) 0.3
(B) 0.4
(C) 0.6
(D) 0.7
(E) 0.8
6. Which of the following solution has the lowest boiling point?
(A) 0.2 m KI
(B) 0.1 m K2SO4
(C) 0.2 m C6H12O6
(D) 0.2 m CH3COOH
7. Which of the following solution has the lowest freezing point?
(A) 1.0 m KI
(B) 0.5 m K2SO4
(C) 1.0 m C6H12O6
(D) 1.0 m CH3COOH
8. Which of the following concentration units will not be affected by temperature? Note that
increasing temperature results in increasing volume.
(A) percent by mass (B) mole fraction
(E) All except choice (C)
(C) molarity
(D) molality
9. What is the percent by mass for a solution made by dissolving 40 g of NaCl in 60 g of water?
(A) 20%
(B) 40%
(C) 60%
(D) 80%
(E) 100%
10. What is the boiling point of a 0.3 m MgCl2 aqueous solution? Assuming that it dissociates
completely. The Kb of water is 0.51oC/m and the boiling point of water is 100oC.
(A) 100.5 oC (B) 100.10 oC (C) 99.8 oC
(D) 99.5 oC
(D) 100.20oC (E) 100.41 oC
11. A solution of 0.85 g of an unknown non-dissociating (i.e non-electrolyte) compound
dissolved in 100.0 g of benzene freezes at 5.16oC. The Kf of benzene is 5.07oC/m. The freezing
point of benzene is 5.45oC. What is the molar mass (g/mol) of the unknown?
(A) 130
(B) 149
(C) 154
(D) 200
(E) 250
Hint: See Example 12.10 (11th ed.)
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12. The average osmotic pressure of blood is 22.7 atm at 25 oC. What concentration (M) of
glucose, C6H12O6, will be isotonic (i.e. same osmotic pressure) with blood to be used in IV
injection?
(A) 0.31
(B) 0.62
(C) 0.93
(D) 1.24
(E) 1.55
th
Hint: see Example 12.9 (11 ed.)
13. The osmotic pressure of blood is 3.5 atm at 25 oC. How much glucose (molar mass 180
g/mol) should be used per liter for an intravenous injection that is to have the same osmotic
pressure as blood?
(A) 54.2 g
(B) 18.4 g
(C) 15.6 g
(D) 20.5 g
(E) 25.8 g
Q14-16. Given the following data for the reaction 2A + B  D + E
Experiment
Initial [A]
Initial [B]
Initial Rate of Formation of D
1
0.080 M
0.034 M
2.2 x 10-4 M.min-1
2
0.080 M
0.017 M
1.1 x 10-4 M.min-1
3
0.16 M
0.017 M
2.2 x 10-4 M.min-1
14. What is the reaction order for A?
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
15. What is the reaction order for B?
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
(D) 3
(E) 4
16. What is the overall reaction order?
(A) 0
(B) 1
(C) 2
Hint: Example 13.3 (11th ed.)
Q17-20. The mechanism for reaction H2(g) + I2(g)  2HI(g) has been proposed:
Step 1
I2(g)  2I(g)
(k1, k -1)
(fast)
Step 2
H2(g) + 2I(g)  2HI(g) (k2)
(slow)
17. Which is the intermediate in this proposed mechanism?
(A) I(g)
(B) H2(g)
(C) HI (g)
(D) All of the above
18. What is the reaction order for I2?
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
19. What is the reaction order for H2?
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
20. What is the overall reaction order?
(A) 0
(B) 1
(C) 2
(D) 3
(E) 4
(E) None of the above.
Q. 21-22. The reaction 4PH3(g)  P4(g) + 6H2(g) is the first order reaction and its rate constant is
0.0198 s-1.
21. If 5.0 moles of PH3 were placed in a 1.0-liter container at that temperature, how many moles
of PH3 would remain after 2.0 minute?
(A) 0.46
(B) 0.25
(C) 0.12
(D) 0.56
(E) 0.36
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Hint: Use formula in Table 13.3 (p. 589) to calculate.
22. What is the half-life for this reaction?
(A) 41 s
(B) 35 s
(C) 18 s
th
Hint: Example 13.6 (11 ed.)
(D) 65 s
(E) 26 s
Q. 23-24. The gas-phase decomposition of NOBr is second order in [NOBr] and its
rate constant is 51 M-1.min-1 at 24oC. Initially there are 0.0092 M NOBr placed in a flask.
23. How many minutes does it take to use up 0.0055 M of this NOBr at such temperature?
(A) 4.9
(B) 1.2
(C) 3.2
(D) 6.0
(E) 8.3
Hint: Use formula in Table 13.3 (p. 589) to calculate. This means the final concentration = 0.0092
– 0.0055 = 0.0037 M.
24. What is the half-life for this reaction?
(A) 4.5 min
(B) 8.5 min
(C) 2.1 min
(D) 3.4 min
th
Hint: Example 13.7 (11 ed.) or Table 13.3 formula.
(E) 1.8 min
25. The gas-phase decomposition of ethyl iodide to give ethylene and hydrogen iodide is a firstorder reaction. C2H5I  C2H4 + HI
At 298 K, the value of k is 3.32 x 10-10 s-1. When the temperature is raised to 313 K, the value of
k increases to 3.13 x 10-9 s-1. What is the activation energy (in kJ) for this reaction?
(A) 819
(B) 332
(C) 116
(D) 232
(E) 131
Hint: Application of Example 13.9
Additional information:
Density = mass/volume
Percent by mass = {mass of solute/mass of solution}  100
Molarity = mole of solute / Liter of solution
Molality = mole of solute / Kg of solvent
R = 8.314 J/mol.K = 0.082 atm/mol.K
Tb = Tb, solution – Tb, solvent = Kb i m
Tf = Tf, solvent – Tf, solution = Kf i m
π = M i  R  T
t1/2 = 0.693/k
ln([A]0/[A]t) = kt.
t1/2 = 1/(k  [A]initial)
1/[A]t –1/[A]o = kt
ln(k2/k1) = (-Ea/R)  (1/T2 –1/T1)
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