Name: __________ ______________
AP* Chemistry: Stoichiometry
1. Which of the following techniques is most appropriate for the recovery of solid KNO3 from
an aqueous solution of KNO3?
2. When hafnium metal is heated in an atmosphere of chlorine gas, the product of the reaction is
found to contain 62.2 percent Hf by mass and 37.4 percent Cl by mass. What is the empirical
formula for this compound?
3. A 2-L container will hold about 4 g of which of the following gases of 0ºC and 1 atm?
A) SO2
B) N2
C) CO2
D) C4H8
E) NH3
4. The atomic mass of copper is 63.55. Given that there are two naturally occurring isotopes of
copper, 63Cu and 65Cu, the natural abundance of the 65Cu isotope must be approximately
5. What mass of Au is produced when 0.0500 mol of Au2S3 is reduced completely with excess
H2?
6. The simplest formula for an oxide of element X (MM = 76.0) that is 24.0 percent oxygen by
weight is
7. A sample of 9.00 grams of aluminum metal is added to an excess of hydrochloric acid. The
volume of hydrogen gas produced at standard temperature and pressure is
8. The weight of H2SO4 (molecular weight 98.1) in 50.0 milliliters of a 6.00-molar solution is
9. A 27.0-gram sample of an unknown hydrocarbon was burned in excess oxygen to form 88.0
grams of carbon dioxide and 27.0 grams of water. What is a possible molecular formula of the
hydrocarbon?
AP* Chemistry: Chemical Reactions and Electrochemistry
Questions 1-4 refer to the reactions represented below.
(A) H2SeO4(aq) + 2 Cl–(aq) + 2 H+(aq) → H2SeO3(aq) + Cl2(g) + H2O(l)
(B) S8(s) + 8 O2(g) → 8 SO2(g)
(C) 3 Br2(aq) + 6 OH–(aq) → 5 Br– (aq) + BrO3– (aq) 3 H2O(l)
(D) Ca2+(aq) + SO42–(aq) → CaSO4(s)
(E) PtCl4(s) + 2 Cl– (aq)→ PtCl62– (aq)
10. A combustion reaction
11. A precipitation reaction
12. A reaction that produces a coordination complex
13. A reaction in which the same reactant undergoes both oxidation and reduction
14.
Cu(s) + 2 Ag+ → Cu2+ + 2 Ag(s)
If the equilibrium constant for the reaction above is 3.7 × 1015, what correctly describes the
standard voltage, E°, and the standard free energy change, ΔG°, for this reaction?
15. When an aqueous solution of NaOH is added to an aqueous solution of potassium
dichromate, K2Cr2O7 the dichromate ion is converted to
16.
M(s) + 3 Ag+(aq) → 3 Ag(s) + M3+(aq) E° = +2.46 V
Ag+(aq) + e– → Ag(s) E° = +0.80 V
According to the information above, what is the standard reduction potential for the half
reaction
M3+(aq) + 3 e- → M(s)?
17. A direct-current power supply of low voltage (less than 10 volts) has lost the markings that
indicate which output terminal is positive and which is negative. A chemist suggests that the
power supply terminals be connected to a pair of platinum electrodes that dip into 0.1-molar KI
solution. Correctly identifiy the polarities of the power supply terminals…
18. When a solution of potassium dichromate is added to an acidified solution of iron(II) sulfate,
the products of the reaction are
AP* Chemistry: Thermochemistry and Thermodynamics
Questions 1-3 refer to the following types of energy.
A) Activation energy
B) Free energy
C) Ionization energy
D) Kinetic energy
E) Lattice energy
19. The energy change that occurs in the conversion of an ionic solid to widely separated
gaseous ions
20. The energy required to form the transition state in a chemical reaction
21. The energy in a chemical or physical change that is available to do useful work
22. 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 atmosphere, PB = 0.5 atmosphere, and PC = 1 atmosphere. At the instant of mixing, whatis true
for the reaction as written?
23.
C2H4(g) + 3 O2(g)  2 CO2(g) + 2 H2O(g)
For the reaction of ethylene represented above, H is –1,323 kJ mol–1. 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.)
24.
H2O(s)  H2O(l)
When ice melts at its normal melting point, 273.16 K and 1 atmosphere, what is true for the
process shown above in terms of G, S, & V?
25. Which of the following must be true for a reaction that proceeds spontaneously from initial
standard state conditions?
A) G° > 0 and Keq > 1
B) G° > 0 and Keq < 1
C) G° < 0 and Keq > 1
D) G° < 0 and Keq < 1
E) G° = 0 and Keq = 1
26. Which property is the same for any two samples of SO2(g) and SO3(g) at the same
temperature?
27. A cube of ice is added to some hot water in a rigid, insulated container, which is then sealed.
There is no heat exchange with the surroundings. What has happened to the total energy and
the total entropy when the system reaches equilibrium?
Energy
Entropy
28.
Cu(s) + 2 Ag+  Cu2+ + 2 Ag(s)
If the equilibrium constant for the reaction above is 3.7 x 1015, which of the following correctly
describes the standard voltage, E°, and the standard free energy change, G°, for this reaction?
29. For which of the following processes would DS have a negative value?
I. 2 Fe2O3(s)  4 Fe(s) + 3 O2(g)
II. Mg2+ + 2 OH¯  Mg(OH)2(s)
III. H2(g) + C2H4(g)  C2H6(g)
30. What describes the direction of changes in enthalpy and entropy for an endothermic
dissolving process of an ionic solute in water at constant temperature?
AP* Chemistry: Kinetics
Questions 1 refers to the following types of energy.
A) Activation energy
B) Free energy
C) Ionization energy
D) Kinetic energy
E) Lattice energy
31. The energy required to form the transition state in a chemical reaction
32. The half-life for radioactive element X is 10.0 min. What weight of X was originally present
in a sample if 40. grams is left after 60. minutes?
33. What has the least effect on the rate of a reaction?
34.
Cl2(g)  2 Cl(g)
Cl(g) + CHCl3(g) → HCl(g) + CCl3(g)
CCl3(g) + Cl(g) → CCl4(g)
fast equilibrium
slow
fast
The reaction between chlorine and chloroform in the gas phase which is known to proceed
according to the mechanism above. According to this mechanism, what is the overall reaction?
35.
Step 1
Step
Step 3
N2H2O2  N2HO2– + H+ (fast equilibrium)
2 N2HO2– → N2O + OH– (slow)
H+ + OH– → H2O (fast)
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:
36. What is a correct comparison of the characteristics of a catalyzed reaction to the
corresponding characteristics of the same reaction without a catalyst present?
I. Their energies of activation are the same.
II. Their enthalpies of reaction are the same.
III. Their free energies of reaction are the same.
Questions 25 - 26
H3AsO4 + 3 I– + 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+]
37. What is the order of the reaction with respect to I–?
38. According to the rate law for the reaction, an increase in the concentration of hydronium ion
has what effect on this reaction?
39. Rate = k[M][N]2
The rate of a certain chemical reaction between substances M and N obeys the rate law above.
The reaction is first studied with [M] and [N] each 1 × 10–3 molar. If a new experiment is
conducted with [M] and [N] each 2 × 10–3 molar, the reaction rate will increase by a factor of
40. What best describes the role of the spark from the spark plug in an automobile engine?
AP* Chemistry: General & Solubility Equilibrium
41. In a saturated solution of Zn(OH)2 at 25ºC, the value of [OH–] is 2.0 × 10–6 M. What is the
value of the solubility product constant, Ksp, for Zn(OH)2 at 25ºC ?
42. Consider the following systems at equilibrium and the stress applied to them. What is the
equilibrium systems shift so that the products were favored?
Equilibrium Stress
I. CO(g) + Cl2(g)  COCl2(g)
add Cl2
II. CO(g) + Cl2(g)  COCl2(g)
remove COCl2
III. PCl3(g) + Cl2(g)  PCl5(g)
remove PCl3
43. Appropriate uses of a visible-light spectrophotometer include which of the following?
I. Determining the concentration of a solution of Cu(NO3)2
II. Measuring the conductivity of a solution of KMnO4
III. Determining which ions are present in a solution that may contain Na+,
Mg2+, Al3+
44. Which of the following is the best statement of LeChatelier's Principle?
I. A system in equilibrium will always remain in equilibrium.
II. A system in equilibrium will not be affected by a change in concentration.
III. A system in equilibrium will respond to a change by shifting in the direction
that reduces the change and restores equilibrium.
45. Equal volumes of 0.10-molar H3PO4 and 0.20-molar KOH are mixed. After equilibrium is
established, the type of ion in solution in largest concentration, other than the K+ ion, is
46. The test for the presence of Ag+ in an unknown solution involves the treatment of the silver
ammonia complex with dilute hydrochloric acid. The appearance of a white precipitate at this
point indicates the presence of silver ion in the original sample. The net ionic equation that
represents this test is
47.
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].
48.
H2C2O4 + 2 H2O  2 H3O+ + C2O42–
Oxalic acid, H2C2O4, is a diprotic acid with K1 = 5 × 10–2 and K2 = 5 × 10–5. What is equal to
the equilibrium constant for the reaction represented above?
49.
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
50.
H2(g) + Br2(g) � 2 HBr(g)
Consider the equilibrium above with Kc = 25 at a certain temperature. A reaction vessel
contains a mixture with the following concentrations : [H2] = 0.10 M, [Br2] = 0.10 M and [HBr] =
0.50 M. What statements concerning the reaction and the reaction quotient, Q, is true?
AP* Chemistry: Gases
Questions 1 - 3 refer to the following gases at 0ºC and 1 atm.
(A) Ne
(B) Xe
(C) O2
(D) CO
(E) NO
51. Has an average atomic or molecular speed closest to that of N2 molecules at 0ºC and 1 atm
52. Has the greatest density
53. Has the greatest rate of effusion through a pinhole
Question 54 refers to the following elements.
A) Lithium
B) Nickel
C) Bromine
D) Uranium
E) Fluorine
54. Is a gas in its standard state at 298 K
55. When a sample of oxygen gas in a closed container of constant volume is heated until its
absolute temperature is doubled, what is also doubled?
56. The density of an unknown gas is 2.00 grams per liter at 3.00 atmospheres pressure and
127°C. What is the molecular weight of this gas?
57. A 2.00-liter sample of nitrogen gas at 27° C and 600. millimeters of mercury is heated until it
occupies a volume of 5.00 liters. If the pressure remains unchanged, the final temperature of the
gas is
58. A sample of 0.010 mole of oxygen gas is confined at 127°C and 0.80 atmosphere. What
would be the pressure of this sample at 27°C and the same volume?
59. A sample of an ideal gas is cooled from 50.0°C to 25.0°C in a sealed container of constant
volume. Which of the following values for the gas will decrease?
I. The average molecular mass of the gas
II. The average distance between the molecules
III. The average speed of the molecules
60. A flask contains 0.25 mole of SO2(g), 0.50 mole of CH4(g), and 0.50 mole of O2(g). The total
pressure of the gases in the flask is 800 mm Hg. What is the partial pressure of the SO2(g) in the
flask?
61. A hydrocarbon gas with an empirical formula CH2 has a density of 1.88 grams per liter at
0°C and 1.00 atmosphere. A possible formula for the hydrocarbon is
62. A sample of 9.00 grams of aluminum metal is added to an excess of hydrochloric acid. The
volume of hydrogen gas produced at standard temperature and pressure is
63. An excess of Mg(s) is added to 100. mL of 0.400 M HCl. At 0ºC and 1 atm pressure, what
volume of H2 gas can be obtained?