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Comparative Study Of Transition Elements Question Paper

Comparative Study Of Transition Elements

Course:Bachelor Of Science

Institution: Kenyatta University question papers

Exam Year:

KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
INSTITUTE OF OPEN LEARNING EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE
SCH 400: COMPARATIVE STUDY OF TRANSITION ELEMENTS
DATE: Friday 19th February, 2010 TIME: 11.00 a.m. – 1.00 p.m. ________________________________________________________________________
Instructions to candidates
Attempt All Questions
1. Explain the following observations
a) Transition elements are hard metals with high electrical and thermal conductivities, high melting points and boiling points.
b) Most transition metals display numerous oxidation states which vary by steps of 1.
c) Transition elements have an unparalleled propensity for forming coordination compounds with Lewis bases.
d) The highest oxidation state possible for iron (Fe) is +6 as in FeO42-. On the other hand the highest oxidation state of osmium (Os) is +8 as in OsO4 and yet they belong in to the same group in the periodic table. (16 marks)
2. State and explain the general trends for each of the following properties down the groups and across the periods of the transition elements.
a) Density
Page 2 of 2
b) Atomic radii
c) Electronegative (10 marks)
3. Give the Oxidation State, d-orbital occupation, co-ordination number and expected magnetic moment of the central metal ion in the following complexes. Draw the expected structure.
a) K4[Fe(C2O4)3]
b) cis-[PtCl2(en)2]Cl
where C2O42- is the oxalate ion and en = ethylenediammine (Fe = 26, Pt = 78).
(12 marks)
4. Briefly describe how you may obtain
(a) Potassium dichromate from the mineral FeCr2O4
(b) CrO3 from the mineral FeCr2O4.
(c) K2CrO4
List any two industrial applications and one laboratory application of chromium metal or its compounds citing the chemical or physical property utilized in each case.
(16 marks)
5. Discuss the following
(a) The contribution of co valency to bonding and stabilization of high oxidation states of transition elements (6 marks)
(b) The stability of group oxidation state of the metals across the first transition series of the periodic table. (6 marks)
(c) Formation of metal-metal bonds in transition metal compounds (4 marks)
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Comparative Study Of Transition Elements Question Paper

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