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Chem 313: Coordination Chemistry Question Paper
Chem 313: Coordination Chemistry
Course:Bachelor Of Science
Institution: Chuka University question papers
Exam Year:2013
CHUKA
UNIVERSITY
UNIVERSITY EXAMINATIONS
THIRD YEAR EXAMINATIONS FOR THE AWARD OF
BACHELOR OF SCIENCE AND BACHELOR OF EDUCATION (SCIENCE)
CHEM 313: COORDINATION CHEMISTRY
STREAMS: BSC &BED (SCIE) Y3S2 TIME: 2 HOURS
DAY/DATE: TUESDAY 23/4/2013 2.30 PM – 4.30 PM
INSTRUCTIONS:
ANSWER QUESTION ONE AND ANY OTHER TWO QUESTIONS.
QUESTION ONE (30 MARKS)
(a) With reasons, explain why mercury and zinc are not classified as transition metal
elements. [2 Marks]
(b) Distinguish between:
(i) Substitutional solid solution and interstitial solid solution. [2 Marks]
(ii) High – spin and low – spin complexes. [2 Marks]
(c) Explain why MnF, may not exist whereas the chemistry of MnO4- is well established. [3 Marks]
(d) Draw both:
(i) Trans and Cis isomers of pt(?NH?_3 )_2 Cl_2 [2 Marks]
(ii) Mer and Fac isomers of MO(thf)_3 ?cl?_3 [3 Marks]
(e) Name the following complexes according to the IUPAC system:
(i) [Co (Cl)_2 (en)_2 ]^+ [2 Marks]
(ii) [(n^5-C_5 H_5 ) (co)_2 Fe (?NH?_2 ?CH?_2 ?CH?_2 ?CH?_3)]?BF?_4 [2 Marks]
(f) Write the formula of chlorotris (triphenyl phosphine) rhodium (i) [2 Marks]
(g) What type of isomerism are possible for complexes with the following molecular formular
(i) [Co(?NH?_3 )_5 Br] 3 ?SO?_4 [1 Mark]
(ii) ?Fe Cl?_2.6H_2 O [1 Mark]
(h) Explain why the density of mercury (13.5g/cm3) is significantly higher than that of cadmium (8.65 g/cm3) whereas the density of cadmium is only slightly greater than that of Zinc (7.14g/cm3)
(i) Experimentally, the magnetic moment of complex [Fe(?OH?_2 )_(6 )]3^+ has been found to be 5.3µB. Determine whether the complex is high-spin or low spin. [4 Marks]
QUESTION TWO (20 MARKS)
(a) A pink solid has the formulaCoCl_3.5?NH?_3.H_2 O. A solution of this salt is also pink and rapidly gives three moles of Agcl on titration with excess silver nitrate solution. When the pink solid is heated, it loses 1mol of H2O to give a purple solid with the same ratio of NH3:Cl:Co.The purple solid, on dissolution and titration with excess AgNO3, produces two moles of AgCl.
(i) Deduce the structures of the two octahedral complexes and provide the IUPAC name for each one of them. [4 Marks]
(ii) Write an equation for the reaction between the pink solid and the excess silver nitrate. [1 Mark]
(iii) Give two possible hydrate isomers of the pink solid present in its aqueous solution. [2 Marks]
(b) Distinguish between a formation constant and a stepwise formation constant. [4 Marks]
(c) The reaction hydrated nickel chloride with excess ammonia solution can be represented by the equation below:
[Ni(?OH?_2 )_6 ]_((aq))^(2+)+6?NH?_(3(aq))?[Ni(?NH?_3 )_6 ]^(2+)+6H_2 O_((1))
Show stepwise formation constants for product complex [Ni(?NH?_3 )_6 ]^(2+) [6 Marks]
QUESTI ON THREE (20 MARKS)
(a) Draw orbital energy – level diagram showing the configuration of d-elections on the complexes [Fe(?OH?_2 )_6 ]^(3+) and [Fe(CN)_6 ]^(-3) [6 Marks]
(b) Compare the magnetic properties of [Fe(H_2 O)]^(3+) with those of [Fe(H_2 O)]^(3+)
[4 Marks]
(c) Which of the two complexes in (b) above will absorb light of the shorter wavelength? Explain. [3 Marks]
(d) Estimate the legend field splitting for:
(i) [Cr(Cl)_6 ]^(3- ) (? max??=740 nm)? [2 Marks]
(ii) [Cr (?NH?_3 )_6 ]^(3+ ) (?ma=460 nm) [2 Marks]
(Given: h=6.626×?10?^(-34), c=2.998 ×?10?^8 ms]
(e) Given suitable conditions, which of the two ligands (chloro and ammine) in d(i) and d(iii) above would displace the other in a reaction? Explain. [3 Marks]
QUESTION FOUR (20 MARKS)
(a) Explain the following terms:
(i) Chelate effect [3 Marks]
(ii) nephelauxetic parameter [3 Marks]
(b) Using Tanabe – sugano diagram for the d3 configuration shown in fig1 and the spectrum given in fig 2.(attached appendix one) deduce the values of ?_0 and B for [Cr(?NH?_3 )_6 ]^(3+)
[6 Marks]
(c) Use the same Tanabe-sugano diagram to predict the energy of the first two spin-allowed quartet band in the spectrum of [?(?OH?_2 )_6]?^(3+) for which ?_0=17600 ?cm?^(-1 ) and B=700?cm?^(-1) [4 Marks]
(d) Write the Russel –saunders term symbols for states with angular momentum quantum number (l,s)
(i) (0,5/2) [2 Marks]
(ii) (3,3/2) [2 Marks]
(iii) (2,1/2) [2 Marks]
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