Chemistry 324 Final Examination
Chemistry 324 Final Examination
Chemistry 324 Final Examination
Chemistry 324
Final Examination
Question Total
1 12
2 12
3 14
4 8
5 10
6 12
7 14
8 12
9 14
10 14
11 14
12 14
Total 150
Chem 324 Final Examination 2010 December 11, 2010 Page 2 of 8
1. Draw the structures of the following complexes or complex ions. [12 pts]
2. Indicate whether each of the following statements is true or false and justify
your answer with a brief explanation. [12 pts]
(a) The pKa of H2O changes from about 14 in free water to between 22 and
24 when it is complexed in [Ti(OH2)6]3+.
(b) VSEPR is usually valid for d10 metal complexes.
(c) Square planar complexes can easily rearrange through a tetrahedral
intermediate at room temperature.
(d) Ligand rearrangement in 6-coordinate complexes often involves either
ligand loss or ligand gain.
(e) Berry pseudo-rotation is a ligand rearrangement that proceeds through a
trigonal prismatic intermediate.
(f) A dodecahedron is normally the least stable 8-coordinate structure and is
therefore very rarely observed.
N terpy N
5. (a) Arrange the following ligands in order of increasing ∆o: bipy, CN-,
H2O, I-. [2 pts]
(b) Predict the magnetic susceptibility behaviour of the ferrocyanide
[Fe(CN)6]4- and [Fe(H2O)6]2+ ions. Give a reason for any difference.
[2 pts]
(c) Suggest a reason why all six Cr-O bonds in the structure of Cr(acac)3
are 1.96 Å while Mn(acac)3 shows four bonds at 1.91 Å and two at
2.09 Å. [3 pts]
(d) Explain why there are virtually no tetrahedral Pd2+ complexes while
Ni2+ can adopt either a square planar or tetrahedral geometry. [3 pts]
(a) Explain why the Laporte symmetry rule is often relaxed (partially
violated) in real complexes. [3 pts]
(b) Explain why the molar absorptivity of [Co(H2O)6]2+ is 10 L mol-1 cm-1
while that for [CoCl4]2- is 600 L mol-1 cm-1. [2 pts]
(c) Predict how many absorption bands there will be (assuming no
overlap) in the UV/Vis spectrum of [Cr(NH3)6]2+. [3 pts]
(d) How does this change if two of the NH3 are replaced by Cl- in trans-
Cr(NH3)4(Cl)2 ? [3 pts]
(e) Explain why, in terms of electronic transitions, substituting two of the
NH3 in [Cr(NH3)6]2+ by bipy to form [Cr(NH3)4(bipy)]2+ leads to a
much more intensely coloured (ε>45,000 L mol-1 cm-1) complex. [3 pts]
9. Zn2+ forms complexes with ligands L1 and L2 (next page) with the following
thermodynamic data:
L1 L2
log K 11.25 15.34
∆Ho (kJ mol-1) -44.4 -61.9
∆So (J mol-1 K-1) 66.5 85.8
Chem 324 Final Examination 2010 December 11, 2010 Page 5 of 8
L1 L2
NH HN NH HN
NH2 H 2N NH HN
(a) Write the mathematical equation for the formation constant K of Zn2+
(aq) with ligand L1 in water. [3 pts]
(b) Suggest reasons why the enthalpy AND entropy are BOTH more
favourable for complexation with L2. [4 pts]
(c) Would you expect complexation with L2 to be more or less favourable
(greater or smaller K value) with Ni2+ instead of Zn2+? Be sure to
consider all factors in arriving at your answer. [HINT: ion size is not a
factor here] [4 pts]
(d) Would you expect complexation with L1 to be more or less favourable
with Hg2+ instead of Zn2+? [3 pts]
10. (a) Comment on the large difference in water exchange rates between
Ru3+(aq) and Fe3+(aq) (a difference of about 108 in rate). Indicate which
is fast and which is slow as part of your answer. [4 pts]
(b) Predict which transition metal ions will have the fastest water
exchange rates of all, giving a rationale for your answer. [3 pts]
(c) The following rate data has been obtained for water substitution by the
ligand specified in [Ru(EDTA)(H2O)]-. Note this is an octahedral Ru3+
complex where one carboxylate arm of the EDTA is not bound to the
metal.
(i) What does the data given suggest about the substitution
mechanism? [4 pts]
Chem 324 Final Examination 2010 December 11, 2010 Page 6 of 8
(ii) If the reverse reaction with water substituting CH3CN has a rate
constant k-1 = 300 M-1 s-1 what is the equilibrium constant Keq
for the following reaction? [3 pts]
k1
[Ru(EDTA)(H2O)]- + CH3CN [Ru(EDTA)(CH3CN)]- + H2O
k-1
(a) Give the most likely product for reaction of this anion with: [3 pts each]
(i) excess ethylene (C2H4)
(ii) excess I-
(iii) excess water
(b) Would the reaction with ethylene proceed faster if the ethylene pressure
was increased? Explain. [3 pts]
(c) Which 195Pt-31P coupling constant would be largest in [Pt(PPh3)3Cl]+?
Explain. [2 pts]
12. Answer the following questions about oxidative addition and reductive
elimination reactions.