Chem 1151 Exam 2 Summer 2005
Name______KEY______
I. Multiple Choice (18 questions @ 3 point = 54 points) Use Scantron form.
1. Which pair of substances will produce a precipitate when equal volumes of aqueous solutions of each are mixed?
A. RbBr and Mg(NO3)2
B. HI and KOH
**C. (NH4)2SO4 and Hg2(CH3CO2)2 see Solubility Rules
D. Pb(NO3)2 + Ba(ClO4)2
2. Zn lies above Cu in the Activity Series. Which statements are true?
false1. Cu will reduce Zn2+
true2. Zn will reduce Cu2+
true3. Zn is the stronger reducing agent
false4. Cu will be oxidized
true5. Cu2+ will be reduced
A. 1 and 2
B. 2 and 3
C. 1, 3 and 4
**D. 2, 3 and 5
3. The oxidation numbers of the underlined element in H2PtCl6, IO3-, and OsO4, respectively are
A. +4, -1, +8
**B. +4, +5, +8
C. +2, -1, +2
D. 0, +6, +8
4. Which chemical equation is incorrectly labeled?
A. HBr(aq) + KOH(aq) à H2O(x) + KBr(aq) acid-base neutralization
B. Hg2(NO3)2(aq) + 2KI(aq) à 2KNO3(aq) Hg2I2(s) precipitation
**C. 2NaNO3(aq) + CuCl2(aq) à 2NaCl(aq) + Cu(NO3)2 redox
D. 2C2H6(g) + 7O2(g) à 6H2O(ℓ) + 4CO2(g) combustion
5. All of the following are strong acids except
**A. H2SO3
B. HNO3
C. HI
D. HClO4
6. Which statement is true about this unbalanced half-reaction?
MnO4-(aq) à MnO42+(aq)
A. Mn is reduced
B. MnO42+(aq) is the oxidizing agent
C. Mn gains electrons
**D. Mn loses electrons
7. Ionic compounds that dissolve completely in water are called
A. Precipitates
**B. Strong electrolytes
C. Weak electrolytes
D. Oxidizing agents
8. Ultraviolet (UV) light has a frequency of 1016 Hz and infrared (IR) light has frequency of 1013 Hz. Which statement is true?
A. λUV > λIR
B. νUV < νIR
**C. EUV > EIR
D. cUV > cIR
9. Which principle or equation expresses the duality of nature?
A. Pauli Exclusion Principle
B. Rydberg-Balmer Equation
C. Heisenberg Uncertainty Principle
**D. deBroglie Equation
10. What combination of quantum numbers is allowed?
n / ℓ / mℓ / ms**A / 4 / 3 / 2 / 1/2
B / 4 / 4 / -4 / -1/2
C / 4 / 0 / 1 / 1/2
D / 4 / -2 / 2 / -1/2
11. The electron configuration [Kr] describes the electron configuration for all of the following except
A. Sr2+
**B. Br
C. Kr
D. Rb+
12. The element in the fourth period with the valance shell 4s2 4p3 is
A. Si
**B. As
C. Tc
D. Sb
13. Many emission lines were observed when the hydrogen atom was excited. Which equation corresponds to the process in which n = 1 = quantum number of the initial state and m = ∞ = quantum number of the final state?
equation**A / H à H+ + e-
B / H+ + e- à H
C / H (1s1) à H(3s1)
D / H+ à H2+ + e-
14. When you go from left to right across a period of the Periodic Table, the effective atomic number, Zeff,
A. not enough information
B. decreases
C. stays the same
**D. increases
15. Which statements are true about Cl- and Cl?
A. Cl- has a smaller radius and a larger first ionization energy.
**B. Cl- has a larger radius and a larger first ionization energy.
C. Cl- and Cl have the same ionization potential but Cl- has a larger radius.
D. Cl- and Cl have the same electron affinity.
16. The electron affinity of sulfur is described by
A. S(g) à S+(g) + e-
B. S+(g) + e- à S(g)
**C. S(g) + e- à S-(g)
D. S-(g) à S(g) + e-
17. The correct order of these species in order of smallest to largest size is
A. As < Br < Sr
**B. Br < As < Sr
C. Sr < Br < As
D. Br < Sr < As
18. Identify the ion with a charge of 2+ and an electron configuration of
[Kr] 5s2 4d10
A. Cd2+
B. Ge2+
C. Hg2+
**D. Sn2+
II. Problems (29 points, show all work)
1. (5) Titration with solutions of KBrO3 can be used to determine the concentration of As(III) in an unknown sample. What is the molarity of As(III) if 33.45 mL of 0.125M KBrO3 is needed to titrate 50.0 mL of the As(III) solution? The balanced chemical equation is
H3AsO3(aq) + BrO3-(aq) à Br -(aq) + 3H3AsO4(aq)
50.0 mL 0.03345mL
M = ? 0.125 M
M x V = # mol solute or M =
# mol solute/V = [(0.03345 x 0.125) x (1 mol H3AsO3/ 1 mol BrO3-)]/0.050 mL
= 0.0836 M
2. (5) Balance this redox reaction in base.
NO3-(aq) + Cu(s) à NO(g) + Cu2+(aq)
Oxidation: [Cu(s) à Cu2+(aq) + 2e- ] x 3
Reduction: [4H+ + NO3-(aq) + 3e- à NO(g) + 2H2O ] x 2
Total: 3Cu(s) + 8H+ + 2NO3-(aq) + 6e- à 3Cu2+(aq) + 6e- + 2NO(g) + 4H2O
Cancel 6e- from each side. Add 8OH- to each side. Cancel 4 water molecules from each side.
Final answer: 3Cu(s) + 4H2O(ℓ) + 2NO3- à 8OH-(aq) + 3 Cu2+(aq) + 2NO(g)
3. (5) Calculate the energy in J/mol for the photons emitted when an electron in the H atom drops from the n = 7 to m = 4 energy level.
1/λ= R [ 1/m2 – 1/n2] = 4.62E+5 1/m
E = Nhν = Nhc/λ = NhcR [ 1/m2 – 1/n2] = 55,273 J/mol
4. (4) Write the electron configurations for
a. Cr Z = 24 [Ar] 4s1 3d5
b. Co2+ Z = 25 [Ar] 3d7
5. (7) Write the equation for each process below
a. first ionization energy of K K(g) à K+(g) + e-
b. bond dissociation energy of Br2 à 2Br(g)
c. lattice energy for K+ and Br - K+(g) + Br -(g) à KBr(s)
d. sublimation of K K(s) à K(g)
e. evaporation of Br2 (ℓ) à Br2 (g)
f. second ionization energy of K K+(g) à K2+(g) + e-
6. (5) True or False
__F__a. Group VIIIA atoms are highly reactive.
_T___b. Group IA atoms are highly reactive.
_F___c. The d-block atoms commonly form anions.
_T___d. All nonmetal elements are p-block atoms.
__T__e. The maximum number of f electrons is 14.
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