Name _____Mr. Perfect_______________________________________ Date _____Sp 12___________
1. Balance the following redox reactions using the half-reaction method. (10 pts)
a)
Cr2O72- + NO2- → Cr3+ + NO3-
[acidic]
6e- + 14H+ + Cr2O72- → 2Cr3+ + 7H2O
3 x (H2O + NO2- → NO3- + 2e-)
8H+ + Cr2O72- + 3NO2- → 2Cr3+ + 3NO3- + 4H2O
b)
Cu + HNO3 → Cu2+ + NO
[basic]
3 x (Cu → Cu2+ + 2e-)
2 x (3e- + 3H+ + HNO3 → NO + 2H2O)
2H2O + 3Cu + 2HNO3 → 3Cu2+ + 2NO + 6OH-
2. Using the spectrochemical series, fill the electrons in the following crystal field diagram for
the following diamagnetic transition metal complex. Is this ligand a strong field ligand or a weak
field ligand? Also predict if the compound is square planar or tetrahedral. (10 pts)
Weak field (high spin) Spectrochemical Series Stong field (low spin)
I-<Br-<Cl-<F-<OH-<H2O<NH3<en< NO2-<CN-<CO
Tetrahedral
Square Planar
[Co(CN)4]Oxidation +3
d6 ion
strong-field ligand
__↑__ __↑__ _____
dxy
dyz
dxz
_____
dx2-y2
_____
dxy
__↑↓_
dz2
__↑↓_ __↑↓_
dz2
dx2-y2
paramagnetic
__↑↓_ __↑↓_
dxz
dyz
diamagnetic
Compound is diamagnetic
Chemistry 102 Exam 3
Name _____Mr. Perfect_______________________________________ Date _____Sp 12___________
3. The complex ion [Co(NH3)5Cl]2+ is violet in solution. Calculate the crystal field splitting
energy in kJ/mol for this ion. (10 pts)
h = 6.626 x 10-34 Js
c = 3.00 x 108 m/s
Absorbed wavelength (nm) Observed Color
6.02 x 1023 ion/mol
400 violet
greenish-yellow
450 blue
yellow
1 nm = 10-9 m
490 blue-green
red
570 yellow-green
violet
580 yellow
dark-blue
600 orange
blue
650 red
green
4. State the oxidation number and the coordination number of the transition metals for each of
the following compounds. (10 pts)
a) Na2[MoO4]
b) K2[Cr(C2O4)2(H2O)]
CN = 4
Ox = +6
CN = 5
Ox = +2
c) [FeEDTA]2-
d) [Co(en)3]3+
CN = 6
Ox = +2
CN = 6
Ox = +3
Chemistry 102 Exam 3
Name _____Mr. Perfect_______________________________________ Date _____Sp 12___________
5. Draw the following transition metal complexes in their correct molecular geometry and state
the hybrid orbital involved in the bonding. Name the molecular geometry shape and label the
bond angles to receive full credit. (10 pts)
a) [NiCN4]2b) [ZnCl4]2Cl
N C
Ni
2-
2-
C N
Zn
C
Cl
N
c) [Fe(H2O)6]PO4
+
OH2
+
H2O
Cl
Cl
N C
4-
d) FeEDTA
+
OH2
Fe
+
+
H2O
+
OH2
OH2
6. Draw the isomers for the following compounds: (10 pts)
a. Coordination Isomers
b. Optical Isomers
[Fe(H2O)5Cl]Br
ZnClNH3BrH2O
+
+
H2O
OH2
4-
+
+
OH2
+
H2O
Fe
H2O
+
+
OH2
OH2
4-
+
+
2-
Zn
+
H2O
OH2
2-
Fe
Cl
+
OH2
OH2
+
Br
H2N
OH2
Zn
Cl
Br
Cl
Br
NH2
* NH3 ligand is not properly displayed.
7. Determine the oxidation and reduction half-reactions for the following voltaic cell. Clearly
label which half-reaction occurs at the anode and which occurs at the cathode. Calculate E°cell
(volts) and G° (kJ) for this cell. (10 pts)
Half-reactions:
Reduction Potentials
Na+ + e- → Na
Al3+ + 3e- → Al
E° (V)
- 2.71
- 1.66
Chemistry 102 Exam 3
F = 96500 J/V mol
oxidation (anode)
reduction (cathode)
Name _____Mr. Perfect_______________________________________ Date _____Sp 12___________
8. Complete the following nuclear reactions. Clearly state the nuclear decay mode to receive full
credit. (10 pts)
Electron Capture
Alpha Particle Decay
a)
b)
x- ray
Negatron Emission
Positron Emission
c)
d)
9. Write a partial decay series for Po-215 undergoing the following sequential decays: (10 pts)
Alpha → negatron → alpha → negatron
10. Calculate Ecell for the following voltaic cell under non-standard conditions: [Fe3+] = 0.001 M
and [Mg2+] = 2.50 M. (10 pts)
2Fe3+(aq) + 3Mg(s) → 2Fe(s) + 3Mg2+(aq)
Nernst Equation
Standard Reduction Potentials
E°
3+
3e- + Fe → Fe
-0.04 V
2+
2e- + Mg → Mg -2.37 V
F = 96500 J/Vmol
- (-2.37 V) = 2.33 V
11. Extra Credit. Draw the ligand ethylenediamine. (5 pts)
CH2
H2N
CH2
NH2
Chemistry 102 Exam 3