Magnetic Moments - Inorganic Chemistry - Exam, Exams for Inorganic chemistry. Aliah University

Inorganic chemistry

Description: Magnetic Moments, Distinguish Square Planar, Octahedral Coordination Compounds, Octahedral Geometry, Coordination Compounds, High Spin, Square Planar Complex, Bromide and Ammonia, Octahedral Transition Metal, Ammonia and Chloride. This is inorganic chemistry past paper from some university. I hope it serve purpose of your searching for exams.
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Spring Examinations 2011 / 2012

Exam Code(s) 3BPC2


Module Code(s) CH319 Inorganic Chemistry


Paper No. I

External Examiner(s) Professor K. Molloy

Internal Examiner(s) Dr. A. Erxleben, Dr. T. Higgins, Dr. L. Jones


Answer four questions. Answer at least one question from each section. All questions carry 25 marks distributed as shown. Leave the first page of

the Answer Book blank and list on it clearly the numbers of the questions



2 hrs

No. of Pages 3 Following this page

Discipline(s) Chemistry

Requirements log tables with periodic table

Section A Answer at least one question from this section

1. Answer each of the following: (a) Show how magnetic moments can be used to distinguish square planar and

octahedral coordination compounds of Ni(II). Explain why the magnetic moments are different. [7 marks]

(b) Show how the Jahn-Teller Theorem can be used to account for the tetragonal distortion from octahedral geometry that is found in coordination compounds of Cu(II) and of high spin Cr(II). [7 marks]

(c) Explain why coordination compounds of Pd(II) and Pt(II) are generally square planar while those of Ni(II) are often octahedral. [6 marks]

(d) Given the task of attempting to synthesise a square planar complex of Ni(II) what ligand(s) would you use. Explain your choice. [5 marks]

2. Answer each of the following: (a) Explain the symbols Eg, T2g, A1g and T1u as they are used in Molecular Orbital

(MO) diagrams. Give one example in each case of either an atomic or molecular orbital for which each of the above symbols are appropriate symmetry labels. [5 marks]

(b) Describe how the ligands bromide and ammonia differ in their bonding with transition metal cations. [5 marks]

(c) Describe the differences in MO diagrams for octahedral transition metal coordination compounds of ammonia and chloride. [10 marks]

(d) Explain why ammonia is higher in the spectrochemical series than water. [5 marks]

Section B Answer at least one question from this section

3. Answer each of the following: (a) Describe the structure of metallo-proteins clearly showing both the protein

structure and how amino acid side chains coordinate metal ions. [8 marks] (b) Describe the role calcium plays in biological systems and illustrate your answer

with an example. [8 marks] (c) Give one example of a zinc metallo-protein. Draw a structure for the active metal

centre and clearly identify the ligands that coordinate the metal. Describe the role this protein plays in biological systems. [9marks]

more on the next page

4. Answer each of the following: (a) The water exchange reaction for [Cr(NH3)5(H2O)]3+ proceeds via an associative

mechanism. (i) Write equations to describe the mechanism of this reaction. (ii) Sketch the reaction profile. Clearly indicate intermediates, transition states

and Gibbs energies of activation. (iii) Explain how you would determine the Gibbs energy of activation. [17 marks] (b) The rate constants for the reduction of [Co(NH3)5(H2O)]3+ and of

[Co(NH3)5(OH)]2+ by [Cr(H2O)6]2+ have been measured. Comment (with reference to possible reaction mechanisms) on the data below. Describe possible reaction mechanisms in detail.

[Co(NH3)5(OH)]2+ + [Cr(H2O)6]2+  [Co(NH3)5(OH)]+ + [Cr(H2O)6]3+ k = 1.5 x 106 M-1 s-1 [Co(NH3)5(H2O)]3+ + [Cr(H2O)6]2+  [Co(NH3)5(H2O)]2+ + [Cr(H2O)6]3+ k = 0.1 M-1 s-1 [8 marks]

Section C Answer at least one question from this section

5. Answer each of the following: (a) Give two examples of ligands which may be classed as: (i) -donors (ii) -donors (iii)-acceptors (iv) -donors and -acceptors [8 marks] (b) Explain how certain ligands can exhibit both -donor and -acceptor behaviour

(as in (iv) above). Indicate how substitution effects influence the -donor and - acceptor strengths. [5 marks]

(c) For each of the following organometallic complexes give the metal valence

electron count and ratify in each case whether the 18-electron rule is obeyed. Show your workings clearly. (i) [(η5-C5H5)Ni(-PPh3)] (ii) [(η5-C5H5)2Co](BF4) (iii)[Cr(η5-C5H5)(η3-allyl)(η4-buta-1,3-diene)] (iv) [RhCl(H)2(η2-C2H4)(PPh3)2]

[12 marks] more on the next page

6. Answer each of the following: In 2005 R. R. Schrock, Y. Chauvin and R. H. Grubbs were awarded a Nobel Prize in Chemistry for their discovery and development of olefin metathesis using novel organometallic complexes as catalysts for this chemistry. (a) Confirm whether the following complex (a Grubbs catalyst used in olefin

metathesis) obeys the 18-electron rule:

[5 marks] (b) Deduce the oxidation state of the Ru metal ion in the above complex. [5 marks] (c) Briefly explain the term olefin metathesis and give three reasons why the

discovery and progression of this chemistry (including the catalysts) was / is so important. Use a sketch to aid your answer. [15 marks]


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