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AP CHEMISTRY – Source: 1999 AP Exam, Also Data Base of MC Questions from
CHAPTER 6, 11-14 PRACTICE TEST:
Thermochemistry, Solutions, Kinetics, Equilibria, Acids/Bases
Prior AP Exams
CHEMISTRY
SECTION I
NO CALCULATORS MAY BE USED WITH SECTION I
Part A
Directions: Each set of lettered choice below refers to the numbered statement immediately following
it. Select the one lettered choice that best fits each statement and then fill in the corresponding oval
on the answer sheet. A choice may be used once, more than once, or not at all in each set.
Directions: Each of the questions or incomplete statements below is followed by five suggested answers or
completions. Select the one that is best in each case and then fill in the corresponding oval on the answer sheet.
CHAPTER 6: THERMOCHEMISTRY
47. CH4(g) + 2 O2(g) ---> CO2(g) + 2 H2O(l); ∆ = - 889.1 kJ
∆Hf° H2O(l) = - 285.8 kJ / mole
∆Hf° CO2(g) = - 393.3 kJ / mole
What is the standard heat of formation of methane, ∆Hf° CH4(g), as calculated from the data above?
(A) -210.0 kJ/mole (B) -107.5 kJ/mole (C) -75.8 kJ/mole
(D) 75.8 kJ/mole
(E) 210.0 kJ/mole
48.Which of the following is a graph that describes the pathway of reaction that is endothermic and has high
activation energy?
A
B
D
E
C
25R.
H2(g) + 1/2 O2(g) ---> H2O(l)
∆H° = x
2 Na(s) + 1/2 O2(g) ---> Na2O(s)
∆H° = y
Na(s) + 1/2 O2(g) + 1/2 H2(g) ---> NaOH(s) ∆H° = z
Based on the information above, what is the standard enthalpy change for the following reaction?
Na2O(s) + H2O(l) ---> 2 NaOH(s)
(A) x + y + z
(B) x + y - z
(C) x + y - 2z
(D) 2z - x - y
(E) z - x - y
30. The energy diagram for the reaction X + Y ---> Z is
shown above. The addition of a catalyst to this reaction would
cause a change in which of the indicated energy differences?
(A) I only
(B) II only
(C) III only
(D) I and II only
(E) I, II, and III
19. Which of the following best describes the role of the spark from the spark plug in an automobile engine?
(A) The spark decreases the energy of activation for the slow step.
(B) The spark increases the concentration of the volatile reactant.
(C) The spark supplies some of the energy of activation for the combustion reaction.
(D) The spark provides a more favorable activated complex for the combustion reaction.
(E) The spark provides the heat of vaporization for the volatile hydrocarbon.
61. C2H4(g) + 3 O2(g) --> 2 CO2(g) + 2 H2O(g) For the reaction of ethylene represented above, ∆H is - 1,323
kJ. What is the value of ∆H if the combustion produced liquid water H2O (l), rather than water vapor H2O(g)?
(∆H for the phase change H2O(g) --> H2O(l) is -44 kJ mol¯1.)
A) -1,235 kJ
(B) -1,279 kJ
(C) -1,323 kJ
(D) -1,367 kJ
(E) -1,411 kJ
CHAPTER 11: SOLUTIONS
10. Use the following answers for questions 10 - 13.
(A) CO32¯
(B) Cr2O72¯
(C) NH4+
(D) Ba2+
(E) Al3+
Assume that you have an "unknown" consisting of an aqueous solution of a salt that contains one of the ions listed
above. Which ions must be absent on the basis of each of the following observations of the "unknown"?
10. The solution is colorless
11. The solution gives no apparent reaction with dilute hydrochloric acid.
12. No odor can be detected when a sample of the solution is added drop by drop to a warm solution of NaOH
13. No precipitate is formed when a dilute solution of H2SO4 is added to a sample of the solution.
37. The molality of the glucose in a 1.0-molar glucose solution can be obtained by using which of the following?
(A) Volume of the solution
(D) Degree of dissociation of glucose
(B) Temperature of the solution
(E) Density of the solution
(C) Solubility of glucose in water
55. At 20. °C, the vapor pressure of toluene is 22 millimeters of mercury and that of benzene is 75 millimeters of
mercury. An ideal solution, equimolar in toluene and benzene, is prepared. At 20. °C, what is the mole fraction of
benzene in the vapor in equilibrium with this solution?
(A) 0.23
(B) 0.29
(C) 0.50
(D) 0.77
(E) 0.83
84. Which of the following aqueous solutions has the highest boiling point?
(A) 0.10 M potassium sulfate, K2SO4
(B) 0.10 M hydrochloric acid, HCl
(C) 0.10 M ammonium nitrate, NH4NO3
(D) 0.10 M magnesium sulfalte, MgSO4
(E) 0.20 M sucrose, C12H22O11
27.
I. Difference in temperature between freezing point of solvent and freezing point of solvent and freezing point
of solution
II. Molal freezing point depression constant, Kf, for solvent
In addition to the information above, which of the following gives the minimum data required to determine the
molecular mass of a nonionic substance by the freezing point depression technique?
(A) No further information is necessary.
(B) Mass of solute
(C) Mass of solute and mass of solvent
(D) Mass of solute and volume of solvent
(E) Mass of solute, mass of solvent, and vapor pressure of solvent
28. Which of the following is probably true for a solid solute with a highly endothermic heat of solution when
dissolved in water?
(A) The solid has a low lattice energy.
(B) As the solute dissolves, the temperature of the solution increases.
(C) The resulting solution is ideal.
(D) The solid is more soluble at higher temperatures.
(E) the solid has a high energy of hydration.
14. Which of the following is lower for a 1.0-molar aqueous solution of any solute than it is for pure water?
(A) pH
(B) Vapor pressure
(C) Freezing point
(D) Electrical conductivity
(E) Absorption of visible light
44. Which of the following solutions has the lowest freezing point?
(A) 0.20 m C6H12O6, glucose (B) 0.20 m NH4Br
(C) 0.20 m ZnSO4 (D) 0.20 m KMnO4 (E) 0.20 m MgCl2
31. If the temperature of an aqueous solution of NaCl is increased from 20 °C to 90 °C, which of the following
statements is true?
(A) The density of the solution remains unchanged.
(B) The molarity of the solution remains unchanged.
(C) The molality of the solution remains unchanged.
(D) The mole fraction of solute decreases.
(E) The mole fraction of solute increases.
43. A sample of 61.8 g of H3BO3, a weak acid is dissolved in 1,000 g of water to make a 1.0-molal solution.
Which of the following would be the best procedure to determine to molarity of the solution? (Assume no
additional information is available.)
(A) Titration of the solution with standard acid
(D) Measurement of the total volume of the solution
(B) Measurement of the pH with a pH meter
(E) Measurement of the specific heat of the solution
(C) Determination of the boiling point of the solution
CHAPTER 12: KINETICS
25. Questions 25-26 H3AsO4 + 3I¯ + 2 H3O+ ---> H3AsO3 + I3¯ + H2O
The oxidation of iodide ions by arsenic acid in acidic aqueous solution occurs according to the stoichiometry
shown above. The experimental rate law of the reaction is: Rate = k [H3AsO4] [I¯] [H3O+]
25. What is the order of the reaction with respect to I¯?
(A) 1
(B) 2
(C) 3
(D) 5
(E) 6
26. According to the rate law for the reaction, an increase in the concentration of hydronium ion has what effect
on this reaction?
(A) The rate of reaction increases.
(B) The rate of reaction decreases.
(C) The value of the equilibrium constant increases.
(D) The value of the equilibrium constant decreases.
(E) Neither the rate nor the value of the equilibrium constant is changed.
28. 2 A(g) + B(g) <===> 2 C(g)
When the concentration of substance B in the reaction above is doubled, all other factors being held constant, it
is found that the rate of the reaction remains unchanged. The most probable explanation for this observation is
that
(A) the order of the reaction with respect to substance B is 1
(B) substance B is not involved in any of the steps in the mechanism of the reaction
(C) substance B is not involved in the rate-determining step of the mechanism, but is involved in subsequent steps
(D) substance B is probably a catalyst, and as such, its effect on the rate of the reaction does not depend on its
concentration
(E) the reactant with the smallest coefficient in the balanced equation generally has little or no effect on the rate
of the reaction
82. Nitramide, N2H2O2, decomposes slowly in aqueous solution. This decomposition is believed to occur according
to the reaction mechanism above. The rate law for the decomposition of nitramide that is consistent with this
mechanism is given by which of the
Step 1) N2H2O2 <===> N2HO2¯ + H+
fast equilibrium
following?
(A) Rate = k [N2H2O2]
Step 2) N2HO2¯ ---> N2O + OH¯
(slow)
(B) Rate = k [N2H2O2] [H+]
Step 3) H+ + OH¯ ---> H2O
(fast)
(C) Rate = (k [N2H2O2]) / [H+]
(D) Rate = (k [N2H2O2]) / [N2HO2¯]
(E) Rate = k [N2H2O2] [OH¯]
57. rate = k[X]
For the reaction whose rate law is given above, a plot of which of the following is a straight line?
(A) [X] versus time (B) log [X] versus time (C) 1/[X] versus time (D) [X] versus 1/time (E) log [X] versus 1/time
58. (CH3)3CCl(aq) + OH¯ ---> (CH3)3COH(aq) + Cl¯ For the reaction represented above, the experimental
rate law is given as follows. Rate = k [(CH3)3CCl]
If some solid sodium hydroxide is added to a solution that is 0.010-molar in (CH3)3CCl and 0.10-molar in NaOH,
which of the following is true? (Assume the temperature and volume remain constant.)
(A) Both the reaction rate and k increase.
(B) Both the reaction rate and k decrease.
(C) Both the reaction rate and k remain the same.
(D) The reaction rate increases but k remains the same.
(E) The reaction rate decreases but k remains the same.
17. Relatively slow rates of chemical reaction are associated with which of the following?
(A) The presence of a catalyst
(D) Strong bonds in reactant molecules
(B) High temperature
(E) Low activation energy
(C) High concentration of reactants
23. The proposed steps for a catalyzed reaction between Ce4+ and Tl+ are represented below. The products of
the overall catalyzed reaction are
Step 1: Ce4+ + Mn2+ ---> Ce3+ + Mn3+
Step 2: Ce4+ + Mn3+ ---> Ce3+ + Mn4+
Step 3: Mn4+ + Tl+ ---> Tl3+ + Mn2+
(A) Ce4+ and Tl+
(B) Ce3+ and Tl3+
(C) Ce3+ and Mn3+
(D) Ce3+ and Mn4+
(E) Tl3+ and Mn2+
49. The isomerization of cyclopropane to propylene is a first-order process
with a half-life of 19 minutes at 500 °C. The time it takes for the partial pressure of cyclopropane to decrease
from 1.0 atmosphere to 0.125 atmosphere at 500 °C is closest to
(A) 38 minutes
(B) 57 minutes
(C) 76 minutes
(D) 152 minutes
(E) 190 minutes
63. The graph above shows the results of a study of the reaction of X with a large
excess of Y to yield Z. The concentrations of X and Y were measured over a period
of time. According to the results, which of the following can be concluded about the
rate of law for the reaction under the conditions studied?
A) It is zero order in [X].
B) It is first order in [X].
C) It is second order in [X].
D) It is the first order in [Y].
E) The overall order of the reaction is 2.
36. The initial-rate data in the table below were obtained for the reaction represented below. What is the
experimental rate la for the reaction?
Experiment Initial [NO]
Initial
Initial Rate of
(A) rate = k[NO] [O2]
1
2
(mol L¯
[O2]
Formation of NO2
(B) rate = k[NO] [O2]
(mol L¯1
(mol L¯1 s¯1)
(C) rate = k[NO]2 [O2]
1
0.10
0.10
2.5 x 10¯4
(D) rate = k[NO]2 [O2]2
(E) rate = k[NO] / [O2]
2
0.20
0.10
5.0 x 10¯4
st
Solution: Can rule our C&D b/c it is 1 order
3
0.20
0.40
8.0 x 10¯3
with respect to NO. Can rule out A & E b/c
it’s NOT 1st order with respect to O2. Answer is B.
CHAPTER 13: EQUILIBRIUM
36. CuO(s) + H2(g) <===> Cu(s) + H2O(g); ∆H = - 2.0 kilojoules
When the substances in the equation above are at equilibrium at pressure P and temperature T, the equilibrium
can be shifted to favor the products by
(A) increasing the pressure by means of a moving piston at constant T
(B) increasing the pressure by adding an inert gas such as nitrogen
(C) decreasing the temperature
(D) allowing some gases to escape at constant P and T
(E) adding a catalyst
57. For the reaction A(g)  B(g) + C(g), the equilibrium constant, Kp, is 2 x 10¯4 at 25 °C. A mixture of the three
gases at 25 °C is placed in a reaction flask and the initial pressures are PA = 2 atm, PB = 0.5 atm, and PC = 1
atm, At the instant of mixing, which of the following is true for the reaction as written?
(A) ∆G < 0
(B) ∆G > 0
(C) ∆S = 0
(D) ∆G° = 0
(E) ∆G° < 0
76. HgO(s) + 4 I¯ + H2O  HgI42¯ + 2 OH¯; ∆H < 0 Consider the equilibrium above. Which of the following
changes will increase the concentration of HgI42¯?
(A) Increasing the concentration of OH¯
(D) Increasing the temperature
(B) Adding 6 M HNO3
(E) Adding a catalyst
(C) Increasing the mass of HgO present
29. In which of the following systems would the number of moles of the substances present at equilibrium NOT be
shifted by a change in the volume of the system at constant temperature?
(A) CO(g) + NO(g) <===> CO2(g) + 1/2 N2(g)
(D) N2O4(g) <===> 2 NO2(g)
(B) N2(g) + 3 H2(g) <===> 2 NH3(g)
(E) NO(g) + O3(g) <===> NO2(g) + O2(g)
(C) N2(g) + 2 O2(g) <===> 2 NO2(g)
48. PCl3(g) + Cl2(g)  PCl5(g) + energy
Some PCl3 and Cl2 are mixed in a container at 200 °C and the system reaches equilibrium according to the
equation above. Which of the following causes an increase in the number of moles of PCl5 present at
equilibrium?
I. Decreasing the volume of the container
II. Raising the temperature
III. Adding a mole of He gas at constant volume
(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III
51. 4 HCl(g) + O2(g)  2 Cl2(g) + 2 H2O(g) Equal numbers of moles of HCl and O2 in a closed system are
allowed to reach equilibrium as represented by the equation above. Which of the following must be true at
equilibrium?
I. [HCl] must be less than [Cl2].
II. [O2] must be greater than [HCl].
III. [Cl2] must equal [H2O].
(A) I only
(B) II only
(C) I and III only
(D) II and III only
(E) I, II, and III
73 R. 2 SO2(g) + O2(g)  2 SO3(g) When 0.40 mole of SO3 and 0.60 mole of O2 are placed in an evacuated
1.00-liter flask, the reaction represented above occurs. After the reactants and the product reach equilibrium
and the initial temperature is restored, the flask is found to contain 0.30 mole of S03. Based on these results, the
expression for the equilibrium constant, Kc, of the reaction is THIS IS A CHAPTER 12-KINETICS QUESTION.
(A) (0.30)2 / [(0.45)(0.10)2]
(D) (0.30) / [(0.45)(0.10)]
2
2
(B) (0 30) / [(0.60)(0.40) ]
(E) (0.30) / [(0.60)(0.40)]
(C) (2 x 0.30) / [(0.45)(2 x 0.10)]
54. 2NO(g) + O2(g) 2 NO2
the value of Keq for the reaction represented above?
A) Decreasing the temperature
D) Increasing the volume of the reaction vessel
B) Increasing the temperature
E) Adding a catalyst
C) Decreasing the volume of the reaction vessel
33. The pH of 0.1-molar ammonia is approximately CH 12
(A) 1
(B) 4
(C) 7
(D) 11
(E) 14
CHAPTER 14: ACIDS/BASES
48. Which of the following ions is the strongest Lewis acid?
(A) Na+
(B) Cl¯
(C) CH3COO¯
(D) Mg2+
49. Each of the following can act as both a Brönsted acid and a Brönsted base EXCEPT
(A) HCO3¯
(B) H2PO4¯
(C) NH4+
(D) H2O
(E) Al3+
(E) HS¯
53. Which, if any, of the following species is in the greatest concentration in a 0.100-molar solution of H2SO4 in
water?
(A) H2SO4 molecules
(B) H3O+ ions
(C) HSO4¯ ions
(D) SO42¯ ions
(E) All species are in equilibrium and therefore have the same concentrations.
75. If the acid dissociation constant, Ka, for an acid HA is 8 x 10¯4 at 25 °C, what percent of the acid is
dissociated in a 0.50-molar solution of HA at 25 °C?
(A) 0.08%
(B) 0.2%
(C) 1%
(D) 2%
(E) 4%
46. As the number of oxygen atoms increases in any series of oxygen acids, such as HXO, HXO2, HXO3, ...., which
of the following is generally true?
(A) The acid strength varies unpredictably.
(B) The acid strength decreases only if X is a nonmetal.
(C) The acid strength decreases only if X is a metal.
(D) The acid strength decreases whether X is a nonmetal or a metal.
(E) The acid strength increases.
55. H2PO4¯ + HBO32¯ <===> HPO42¯ + H2BO3¯
The equilibrium constant for the reaction represented by the equation above is greater than 1.0. Which of the
following gives the correct relative strengths of the acids and bases in the reaction?
56. A 0.20-molar solution of a weak
monoprotic acid, HA, has a pH of 3.00.The
ionization constant of this acid is
(A) 5.0 x 10¯7
(B) 2.0 x 10¯7
6
(C) 5.0 x 10¯
(D) 5.0 x 10¯3
(A)
(B)
(C)
(D)
(E)
Acids
H2PO4¯ > H2BO3¯
H2BO3¯ > H2PO4¯
H2PO4¯ > H2BO3¯
H2BO3¯ > H2PO4¯
H2PO4¯ = H2BO3¯
and
and
and
and
and
Bases
HBO32¯ > HPO42¯
HBO32¯ > HPO42¯
HPO42¯ > HBO32¯
HPO42¯ > HBO32¯
HPO42¯ = HBO32¯
(E) 2.0 x 10¯3
22. HSO4¯ + H2O <===> H3O+ + SO42¯ In the equilibrium represented above, the species that act as bases
include which of the following?
I. HSO4¯
II. H2O
III. SO42¯
(A) II only
(B) III only
(C) I and II
(D) I and III
(E) II and III
31. R. H2C2O4 + 2 H2O <===> 2 H3O+ + C2O42¯ Oxalic acid, H2C2O4, is a diprotic acid with K1 = 5 x 10¯2
and K2 = 5 x 10¯5. Which of the following is equal to the equilibrium constant for the reaction represented
above?
(A) 5 x 10¯2
(B) 5 x 10¯5
(C) 2.5 x 10¯6
(D) 5 x 10¯7
(E) 2.5 x 10¯8
61. A 1-molar solution of which of the following salts has the highest pH ?
(A) NaNO3
(B) Na2CO3
(C) NH4Cl
(D) NaHSO4
(E) Na2SO4
66. What is the pH of a 1.0 x 10¯2-molar solution of HCN? (Ka = 4.0 x 10¯10.)
(A) 10
(B) Between 7 and 10
(C) 7
(D) Between 4 and 7
(E) 4
64. The net ionic equation for the reaction that occurs during the titration of nitrous acid with sodium hydroxide is
(A) HNO2 + Na+ + OH¯ ---> NaNO2 + H2O
(D) HNO2 + H2O ---> NO2¯ + H3O+
+
(B) HNO2 + NaOH ---> Na + NO2¯ + H2O
(E) HNO2 + OH¯ ---> NO2¯ + H2O
(C) H+ + OH¯ --->H2O
74. How many moles of NaF must be dissolved in 1.00 liter of a saturated solution of PbF2 at 25 °C to reduce
the [Pb2+] to 1 x 10¯6 molar? (Ksp of PbF2 at 25 °C = 4.0 x 10¯8)
(A) 0.020 mole
(B) 0.040 mole
(C) 0.10 mole
(D) 0.20 mole
(E) 0.40 mole
63. On the basis of the information below, a buffer with a pH = 9 can best be made by using
(A) pure NaH2PO4
(B) H3PO4 + H2PO4¯ (C) H2PO4¯ + PO43¯ (D) H2PO4¯ + HPO42¯ (E) HPO42¯ + PO43¯
19. In the titration of a weak acid of unknown concentration with a standard solution of a strong base, a pH
meter was used to follow the progress of the titration. Which of the following is true for this experiment?
(A) The pH is 7 at the equivalence point.
(B) The pH at the equivalence point depends on the indicator used.
(C) The graph of pH versus volume of base added rises gradually at first and then much more rapidly.
(D) The graph of pH versus volume of base added shows no sharp rise.
(E) The [H+] at the equivalence point equals the ionization constant of the acid.
35. When phenolphthalein is used as the indicator in a titration of an HCl solution with a solution of NaOH, the
indicator undergoes a color change from clear to red at the end point of the titration. This color change occurs
abruptly because
(A) phenolphthalein is a very strong acid that is capable of rapid dissociation
(B) the solution being titrated undergoes a large pH change near the end point of the titration
(C) phenolphthalein undergoes an irreversible reaction in basic solution
(D) OH¯ acts as a catalyst for the decomposition of phenolphthalein
(E) phenolphehalein is involved in the rate-determining step of the reaction between H3O+ and OH¯
66. MnS(s) + 2 H+ <===> Mn2+ + H2S(g) At 25 °C the solubility product constant, Ksp, for MnS in 5 x 10¯15
and the acid dissociation constants K1 and K2 for H2S are 1 x 10¯7 and 1 x 10¯13, respectively. What is the
equilibrium constant for the reaction represented by the equation above at 25 °C?
(A) 1 x 10¯13 / 5 x 10¯15
(D) 5 x 10¯15 / 1 x 10¯20
15
7
(B) 5 x 10¯ / 1 x 10¯
(E) 1 x 10¯20 / 5 x 10¯15
7
20
(C) 1 x 10¯ / 5 x 10¯
ANSWERS:
CH: 6: THERMOCHEMISTRY
47. C
48. A
25. D
30. D
19. C
61. E
CH 11: SOLUTIONS
10. B
11. A
12. C
13. D
37. E
55. D
84. A
27. C
28. D
14. C
44. E
31. C
43. D
CH 12: KINETICS
25. A
26. A
28. C
82. C
57. B
58. C
17. D
23. B
49. B
63. A
36. B
CH 13: EQUILIBRIUM
36. C
57. B
76. B
29. E
48. A
51. D
73. A
54. B
CH 14: ACID/BASE
48. E
49. C
53. B
75. E
46. E
55. A
56. C
22. E
31. C
61. B
66. D
64. E
74. D
63. D
19. C
35. D
66. C
FREE RESPONSE
PART A: Calculators and Equation Tables may be used.
C6H5NH2(aq) + H2O(l)  C6H5NH3+ (aq) + OH- (aq)
1. Aniline, a weak base, reacts with water according to the reactions represented above.
(a) Write the equilibrium constant expression, Kb, for the reaction represented above
(b) A sample of aniline is dissolved in water to produce 2.0 mL of a 0.10 M solution. The pH of the
solution is 8.82. Calculate the equilibrium constant, Kb, for this reaction.
(c) The solution prepared in part (b) is titrated with -.10 M HCl. Calculate the pH of the solution
when 5.0 mL of the acid has been added.
(d) Calculate the pH at the equivalence point of the titration in part (c).
(e) The pKa values for several indicators are given below. Which of the indicators listed is most
suitable for this titration? Justify your answer.
Indicator
pKa
Erythrosine
3
Litmus
7
Thymolphthalein
10
Br-(aq) + BrO3- (aq) + 6H+ (aq)  3Br2(l) + 3H2O(l)
2. In a study of the kinetics of the reaction represented above, the following data were obtained at
298K.
Rate of
Experiment Initial [Br-]
Initial [BrO3-] Initial [H+] Diappearance
(mol L-1)
(mol L-1)
(mol L-1)
of BrO3(mol L-1 s-1)
1
0.00100
0.00500
0.100
2.50 x 10-4
2
0.00200
0.00500
0.100
5.00 x 10-4
3
0.00100
0.00750
0.100
3.75 x 10-4
4
0.00100
0.01500
0.200
3.00 x 10-3
(a) From the data given above, determine the order of the reaction for each reactant listed below.
Show your reasoning.
(i) Br(ii) BrO3(iii) H+
(b) Write the rate law for the overall reaction.
(c) Determine the value
of the specific rate
constant for the
reaction at 298 K.
Include the correct
units.
(d) Calculate the value of
the standard cell
E⁰ (V)
Half-reaction
Br2(l) + 2 e -  2 Br-(aq)
+1.065
BrO3- (aq) + 6H+ (aq) + e- 1/2 Br2(l) + 3H2O(l)
+1.52
potential, E⁰, for the reaction using the information in the table below.
(e) Determine the total number of electrons transferred in the overall reaction.
6. For each of the following, use appropriate chemical principles to explain the observation. Include
chemical equations as appropriate.
(a) In areas affected by acid rain, statues and structures made of limestone (calcium carbonate) often
show signs of considerable deterioration.
(b) When table salt (NaCl) and sugar (C12H22O11) are dissolved in water, it is observed that
(i) both solutions have higher boiling points than pure water, and
(ii) the boiling point of 0.10 M NaCl (aq) is higher than that of 0.10 M C12H22O11(aq).
(c) Methane gas does not behave as an ideal gas at low temperatures and high pressures.
(d) Water droplets form on the outside of a beaker containing an ice bath.
3. (a)Show the complete equation of the combustion of the flammable gas butane, C4H8.
(b) Given the following table of bond energies, estimate the enthalpy change, H, for the reaction in
3a.
Bond energies (kJ.mol)
C-H 413
C-O 358
O=O 495
C-C
347
C=O 799
C=C 614
H-O 467
C=C 839
H-H 432
(c) Often the heat of reaction enthalpy calculated from bond energies differs by 10-20% or moe fom
the laboratory determined values. Suggest why this is so.
(d) Show two of the several isomers of butane.
(e) Draw a Lewis structure diagram of butane. Indicate the kinds of hybridization of carbon in this
molecule. Indicate all bond angles.