New Jersey Science League
Chemistry II Exam April 2005
Answer the following questions on the answer sheet provided. Each correct response is worth 4 points. Use the
letters in parentheses for your answers. Choose the letter that best completes or answers the item. Be certain that
erasures are complete. Please PRINT your name, school, area, and which test you are taking on the scan-tron.
1. The figure to the right was generated from data obtained
for the decomposition of dinitrogen monoxide in which
nitrogen and oxygen are produced. Which of the following
statements is false based on the information given?
A.
B.
C.
D.
Nitrogen gas is formed at twice the rate of oxygen.
The reaction rate is directly proportional to [N2O].
The slope of the line corresponds to -k.
The half-life of the reaction decreases with
decreasing concentration of N2O.
E. None of the above
2. Consider the following elementary reversible reaction:
kf
A(g) + B(g) ↔ C(g) + D(g)
kr
Which of the following expressions is mathematically equivalent to the equilibrium constant Kc for the
reaction. kf and kr are the specific rate constants for the forward and reverse reactions, respectively.
A. [A][B]
B. kf • kr
C. kf
D. kr
E. kf[A][B]
[C][D]
kr
kf
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3. At 25oC, 0.0168 g CaF2 (molar mass = 78.1g) will dissolve in 1 liter of water. The solubility
product constant of CaF2 at this temperature is most nearly
A. 4.0 x 10-11
B. 9.9 x 10-12
C. 4.6 x 10-8
D. 4.7 x 10-6
E. 4.5 x 10-8
4. The autoionization of water is an endothermic process. Which of the following statements is true
regarding water at 60oC?
A. pH = pOH = 7
B. pH > 7, pOH < 7
C. pH < 7, pOH > 7
D. pH = pOH < 7
E. pH = pOH > 7
5. Which is the weakest base among the following?
A. FB. ClC. H2O
D. OH-
E. SO42-
6. When a beta-particle is emitted from the nucleus, the original element has its
A. number of protons decreased by one while mass number remains the same.
B. number of protons decreased by one and the number of neutrons increased by one.
C. number of protons increased by one and the number of neutrons increased by one.
D. number of protons decreased by one and the number of neutrons decreased by one.
E. number of protons increased by one and the number of neutrons decreased by one.
7. Sodium acetate is dissolved in water. Which of the following is true regarding the aqueous
solution formed?
A. Undissociated HC2H3O2 is present.
D. The resulting solution is somewhat acidic
B. The sodium ion acts as a base.
E. none of the above
+
C. [Na ] is exactly equal to [C2H3O2 ]
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Information needed for problems #8 and #9
Acid
Acid Dissociation Constant
HClO2
1.2 x 10-2
HC3H5O3
1.4 x 10-4
HC2H3O2
1.8 x 10-5
H3PO4
Ka1 = 7.5 x 10-3
Ka2 = 6.2 x 10-8
Ka3 = 4.8 x 10-13
8. Which one of the following systems is the best choice to make a buffer at pH 3.5?
A. HClO2, NaClO2
B. HClO2, NaCl
C. HC3H5O3, NaC3H5O3
D. HC2H3O2, NaC2H3O2
E. HC2H3O2, NaCl
9. Which one of the following lists the ions present in a 5 M H3PO4 solution in order of decreasing
concentration? (OH- is excluded from list; H+ represents hydronium ion)
A. H+ and H2PO4-, HPO42-, PO43D. H+, PO43-, HPO42-, H2PO4+
32B. H , PO4 , H2PO4 , HPO4
E. H2PO4-, HPO42-, PO43-, H+
3+
2C. PO4 , H , H2PO4 , HPO4
10. Which of the following cannot be an oxidizing agent?
A. O2
B. O2C. Cl2
D. MnO4-
E. Cr2O72-
11. A current of 2.50 A is delivered to an electrolytic cell for 1.50 hours. How many grams of Cu
can be obtained from excess CuCl2?
A. 428,000
B. 8.88
C. 0.740
D. 119
E. 4.44
12. Consider the following balanced cell reaction: (electrodes used are Fe and Pt)
2 MnO4- (aq) + 5 Fe(s) + 16 H+(aq)  5 Fe2+(aq) + 2 Mn2+(aq) + 8H2O(l) where o = 1.95 V
Select all of the following statements that are true .
I. The half reaction occurring at the anode is Fe(s)  Fe2+(aq) + 2eII. The initial concentration of MnO4- is 2M
III. The iron electrode is consumed during the reaction.
IV. Electrons flow from the Fe electrode to the Pt electrode.
A. all of the above
B. I, II, III
C. I, III, IV
D. II, III, IV
E. I, III only
13. Consider the dimerization reaction of NO2:
2 NO2(g) ↔ N2O4 (g)
Kc = 3.3 at 100oC
Which of the following statements are true regarding this reaction at 100oC?
I.
The term (TSo) is positive.
II.
The sign of Ho is negative.
III.
At very low temperatures the reverse reaction becomes spontaneous.
A. I only
B. II only
C. III only
D. I, II only
E. II, III only
14. The half-life of molybdenum-99 is 67.0 hours. The amount of molybdenum-99 that remains from
a 1.000 mg sample after 33.5 hours has elapsed is most nearly
A. 0.75 mg
B. 0.71 mg
C. 0.67 mg
D. 0.63 mg
E. 0.58 mg
15. Sodium-22 decays by positron production. The daughter nuclide formed is
A. 22Ne
B. 22Mg
C. 21Na
D. 21Mg
E. 23Na
16. What is the systematic name for the coordination compound [Co(NH3)5Cl]Cl2?
A. pentaammoniachlorinecobalt(III) chloride
B. pentaammoniachlorinecobalt(II) chloride
C. pentaamminechlorocobalt(III)chloride
D. cobalt(III) pentaammoniachlorine chloride
E. pentaammoniumchlorinecobalt(III) chloride
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17. What is the oxidation number of platinum in the coordination compound [Pt(H2O)(CO)3]Br2
A. +1
B. +2
C. +3
D. +4
E. +5
18. Consider the reaction: 2 NO2 (g) + F2 (g)  2 NO2F(g)
Which of the following mechanisms is consistent with the experimentally determined rate law?
Rate = k [NO2][F2]
A. slow: NO2  NO + O
fast: O + F2  OF + F
fast: NO + OF  NO2F
B. slow: F2  2 F
fast: F + NO2  OF + NO fast: NO + OF  NO2F
C. slow: F2  2 F
fast: 2 F + 2 NO2  2 NO2F
D. fast: NO2 + F2  NO2F + F slow: F + NO2  NO2F
E. slow: NO2 + F2  NO2F + F fast: F + NO2  NO2F
19. A 0.200 g sample of a compound containing only carbon, hydrogen and oxygen is burned in air,
and 0.357 g CO2 and 0.146 g H2O are collected. What is the empirical formula of the original
compound?
A. C2H6O
B. CH2O
C. C3H6O2
D. CH4O
E. C3H8O
20. At a particular temperature, Kp = 0.25 atm for the reaction A(g) ↔ 2B(g)
4.5 atm of gas A is introduced into a flask and is allowed to reach equilibrium. What is the
equilibrium pressure of gas B?
A. 1.0 atm
B. 2.0 atm
C. 3.0 atm
D. 4.0 atm
C. 5.0 atm
21. Which one of the following 1 M solutions would have the lowest conductivity?
A. NaC2H3O2
B. CaCl2
C. HNO3
D. KBr
E. HC2H3O2
22. Consider the reaction: N2(g) + 3 H2(g) ↔ 2 NH3(g)
H = -92 KJ
Select all of the following changes to the equilibrium situation that will result in an increase in the
number of moles of H2(g) present at equilibrium.
I. Removing N2(g) from the reaction chamber.
II. Increasing the temperature of the reaction chamber.
III. Increasing the volume of the reaction chamber.
A. I only
B. II only
C. I, II only
D. I, III only
E. I, II, III
23. In order to determine the molar mass of butane, a student collected gaseous butane by water
displacement by releasing butane from a lighter while it was immersed underwater (as shown). The
lighter was weighed before and after use. Which of the following would result in an experimentally
determined molar mass greater than the accepted value?
A. The lighter was slightly wet when reweighed.
B. The student failed to account for the water vapor pressure in their calculations.
C. The water level in the collection tube was above that in the bucket and no correction
was made.
D. The student failed to notice an air bubble that was present in the collection tube
prior to collecting the butane.
E. None of the above.
24. The acid dissociation constant (Ka) for HCN dissolved in water is 6.2 x 10-10. What is the value
of Kb for CN-?
A. 1.6 x 109
B. 1.6 x 10-5
C. 6.2 x 104
D. 6.2 x 10-24
E. 6.2 x 10-10
25. Of the following hydrocarbons, select the one that has the lowest molar mass that exhibits
structural isomerism.
A. CH4
B. C2H6
C. C3H8
D. C4H10
E. C5H12
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Chemistry II
April 05 Answer Key
1
B
6
E
11 E
16 C
21 E
2
C
7
A
12 C
17 B
22 E
3
A
8
C
13 D
18 E
23 E
4
D
9
A
14 B
19 C
24 B
5
B
10 B
15 A
20 A
25 D
CHEMISTRY 11
JANUARY: matter and measurement, atomic theory(sub-atomic particles, atomic masses), chemical formulas,
chemical equations(mole relationships, mass-mass problems)¸ stoichiometry of redox solutions, stoichiometry of
molar solutions, electronic structure and periodic table.
FEBRUARY: chemical bonding, electronegativity, Lewis structures, molecular geometry, polarity of molecules,
hybridization, liquids, solids, vapor pressure, intermolecular forces, phase changes, gases, plus January topics.
MARCH: thermochemistry( enthalpy, Hess’s Law, heats of formation, bond energies, calorimetry), molecular
orbitals, non-metals, metals, solutions, colligative properties, descriptive chemistry of the elements, plus Jan
and Feb topics.
APRIL: chemical equilibrium, rates of reactions, reaction mechanisms, acids, bases, and salts, Ka, Kb, Ksp,
buffers, coordination compounds, redox, voltaic cells, Nernst equations, S, H, G, nuclear chemistry, organic
chemistry, descriptive chemistry of the elements, plus Jan, Feb., and Mar topics.
Testing Dates NJSL 2006
THURSDAY JANUARY 12, 2006
THURSDAY FEBRUARY 9, 2006
THURSDAY MARCH 9, 2006
THURSDAY APRIL 13, 2006
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