SI: Exam 3 Review
1. Balance the following reaction in base.
UO2+ (aq) + Cr2O72- (aq) → Cr3+ (aq) + U3O8
2. a. Write the balanced equation for the spontaneous reaction that occurs for the two half reactions
below. Assume standard conditions.
Fe3+ (aq) + 3 e- → Fe (s)
E° = -0.04 V
2+
Pb (aq) + 2 e- → Pb (s)
E° = -0.12 V
b. Calculate Eᵒcell.
c. Calculate ΔG.
d. Calculate K.
3. Balance the following redox reaction under acidic conditions:
ClO3- (aq) + N2H4 (l)  NO (g) + Cl- (aq)
4. Electrolysis of molten MgCl2 is the final production step in isolation of magnesium from seawater.
Assuming that 45.6 g of Mg metal forms,
a. How many moles of electrons are required?
b. How many coulombs are required?
c. How many amps will produce this amount in 3.5 hours?
5. Sketch the d-orbital energy level diagram for [FeBr6]3–. Include the orbital labels and place the
electrons in the diagram accordingly. Predict the color and magnetic behavior of the complex.
a. What is the oxidation state of Fe?
b. What is the color of the complex?
c. How many unpaired electrons are in the complex?
6. The solubility of Al(OH)3 is 5.65x10-4 mol/L. What is the Ksp?
7. 7. Fill in the blanks in the following table.
Name
Potassium hexacyanochromate(III)
Formula
[Pt(en)2][PtCl4]
Tetraamminezinc sulfate
[Cr(en)3](ClO4)3
K4[Mn(CN)6]
8. Assuming standard conditions, complete the table at the bottom of the page for the given unbalanced
reaction. Comment on its spontaneity.
KClO3 (s)
KCl (s)
O2 (g)
ΔH°(kJ/mol)
-397.73
-436.68
S° (J/mol•K)
143.1
82.56
205.07
_____ KClO3 (s) → ____ KCl(s) + ____ O2 (g)
ΔH°reaction
Answer:
ΔS°reaction
ΔG°reaction or
ΔS°universe
Spontaneous or
Non-spontaneous;
9. A voltaic cell consists of a nickel electrode in an aqueous solution of Co(NO3)2 and a chromium
electrode an aqueous solution of Al(NO3)3.
Co2+ (aq) + 2 e-  Co (s)
Eᵒ = -0.28 V
3+
Al (aq) + 3 e  Al (s)
Eᵒ = -1.66 V
a. What balanced, spontaneous reaction occurs in the cell under standard conditions (include all physical
states)?
b. Write the voltaic cell notation for the above cell.
c. What is the voltage of the cell under standard conditions?
d. Calculate the potential of the same cell made with 5.5 M Co(NO3)2 and 5.5x10-2 M Al(NO3)3.
10. Use the standard reduction potentials below to determine which element or ion is the strongest
reducing agent.
Fe2+ (aq) + 2 e- Fe (s)
E° = –0.44 V
Cr2+ (aq) + 2 e → Cr (s)
E° = –0.91 V
2+
Cu (aq) + 2 e- → Cu (s)
E° = +0.34 V
a. Fe2+
b. Fe
c. Cr2+
d. Cr
e. Cu2+
f. Cu
11. Which of the following ions have a d6 electron configuration?
a. Cr2+
b. Ni+
c. Co3+
d. Mn2+
12. Which are true of the role of a salt bridge?
a. To maintain electrical neutrality
b. To make the voltaic cell spontaneous
c. To add negative ions to the cathode
d. To add negative ions to the anode
13. True or false, correct the false.
a. Oxidation occurs at the anode.
b. Reduction occurs at the anode.
c. Electrons flow from the negative half-cell to the positive half-cell.
14. Predict the signs of ΔH° and ΔS° for the evaporation of water.
a. ΔH° > 0 and ΔS° < 0
b. ΔH° > 0 and ΔS° > 0
c. ΔH° < 0 and ΔS° > 0
d. ΔH° < 0 and ΔS° < 0
15. Which reaction is likely to have a negative change in entropy?
a. 2 NH3 (g) → N2 (g) + 3 H2 (g)
b. CaO (s) + CO2 (g) → CaCO3 (s)
c. N2O4 (g) → 2 NO2 (g)
d. 2 C2H6 (g) + 7 O2 (g) → 4 CO2 (g) + 6 H2O (g)
16. The free energy change for a given reaction is -198.3 kJ/mol at 25°C. What is the equilibrium
constant for this reaction?
a. 9.9 x 1079
b. 1.08
c. 5.5 x 1034
d. 1.20
17. Calculate ΔG° for the following equation at 298K given K = 0.36.
N2O4 (g) → 2 NO2 (g)
a. 2.53 kJ/mol
b. 2.88 kJ/mol
c. 4.70 kJ/mol
d. 27.8 kJ/mol
18. Consider the following unbalanced equation. What species is the reducing agent?
I- (aq) + MnO4- (aq)  IO3- (aq) + MnO2 (s)
(acidic conditions)
a. I (aq)
b. MnO4 (aq)
c. IO3 (aq)
d. MnO2 (s)
19. What happens to solubility when H3O+ is added to NaI?
a. increases
b. decreases
c. remains the same
20. The first law of thermodynamics states?
a. a perfect crystal has zero entropy at absolute zero
b. all real processes occur spontaneously to increase entropy of the universe
c. energy is conserved
21. Ligands that promote high spin configurations are termed
a. anions
b. neutral
c. weak field d. strong field
22. An octahedral complex ion containing only the ligand phenanthroline is found to be blue in color.
This indicates that phenanthroline is a:
a. strong field ligand
b. “mid” field ligand
c. weak field ligand
23. What is the oxidation number of Cu in [Cu(CN)4]3-?
a. 3+
b. 2+
c. 3d. 1+
24. What is the coordination number of [Co(en)3]?
a. 2
b. 6
c. 3
d. 4
25. What color would you predict [Fe(CN)6]4- to be?
a. red
b. green
c. blue