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Chemical Bonding And Structure Question Paper
Chemical Bonding And Structure
Course:Bachelor Of Science In Analytical Chemistry
Institution: Jomo Kenyatta University Of Agriculture And Technology question papers
Exam Year:2011
UNIVERSITY EXAMINATION 2011/2012.
YEAR ONE SEMESTER TWO EXAMINATION FOR THE DEGREE OF BACHELOR
OF SCIENCE.
SCH 2101: CHEMICAL BONDING AND STRUCTURE.
DATE:DECEMBER 2011 TIME:2 HOURS.
INSTRUCTIONS:ANSWER QUESTION ONE AND ANY OTHER TWO QUESTIONS. USE THE UNIVERSAL PERIODIC TABLE.
QUESTION ONE(30 MRKS)
A.With examples explain the following:
(i) Co-ordinate covalent bond.(2 mrks)
(ii) Hydrogen bonding.(2 mrks)
(iii) Resonance.(2 mrks)
(iv)Electronegativity (2 mrks)
(v)Intermolecular force.(2 mrks)
(b) Write Lewis structures for the following species showing your working;
(i) SCN-( 2 mrks)
(ii)CO( 2 mrks)
(iii)PCl5(2 mrks)
(C)List the intermolecular forces that you will expect between the following species\
(i)H2O molecules(2 mrks)
(ii)Br2 molecules(2 mrks)
(iii) HCl and H2O(2 mrks)
(iv) H2O and Cl-( 2mrks)
(D) A 25 ml sample of 1.00 MKBr and a 75 ml sample of 0.8 MKBr are mixed. The solution is the heated to evaporate water until the solution volume is 50 ml. Calculate the molarity of the final solution(3 mrks)
(i) What mass of NaCl is required to precipitate all the silver ions from 20 ml of 0.1NagNO3 solution?(3 mrks)
QUESTION TWO(20 MRKS)
(A)(i) Explain what is meant by ionization energy.(1 mrk)
(ii)Why are ionization energies always positive quantities?(2 mrks)
(iii)Why does Lithium have higher ionization energy than Na ?( 2 mrks)
(B) The cyanate ion (NCO-) has three possible Lewis structures. Draw the structures and indicate the most preferred form.(4 mrks)
(c)Hydrogen and Carbon have electronegativity values of 2.05 and 2.28 respectively. Estimate the bond energy for C-C bond given the following bond energies.
C-H 414KJ/Mol
H-H 437KJ/Mol
(D) (i) State the Octet rule.(1 mrk)
(ii)With examples show under which conditions the Octet rule can be violated.( 3mrks)
(iii)Explain the difference in the geometry for CH4 and H2O molecules.(4 mrks)
QUESTION THREE.(20 MRKS)
(a) Draw a well labeled molecular orbital energy level diagram for the CO molecule. Calculate the bond order for the species CO, CO+ and CO. (8 mrks)
(b) Predict the magnetic properties of the three species in (a) above, giving a reason in each case. (C6O8) (3 mrks)
(c) Derive the hybridization of the central atom involved in forming each of the following species. Also draw and describe their geometries.(9 ,mrks)
(i) C2H2
(ii) SF6
(iii) [BH4]-
(6C, 1H, 16S, 9F, 5B)
QUESTION FOUR.
(A)Draw the most predominant resonance structures for SO32- (16S, 8O) (3 mrks)
(B)Predict and draw the shape of the Al2Cl6 molecule. (13Al, 17Cl) ( 2 mrks)
(C)Explain why metals conduct electricity but their ionic salt solids do not.( 2mrks)
(D) Explain why BF3 is non-polar, yet the B-F bond is polar.(5B 9F) (2mrks)
(E) 8g of NaOH pellets were dissolved in a liter of solution with distilled water. In order to standardize this solution, 10.0 mls of an acid solution containing 19.6 g of H2SO4 per liter completely neutralized 25 mls of the NaOH solution.
(i)Why was it necessary to standardize the NaOH solution, even though the original concentration was known? (2 mrks)
(ii)Write a balanced chemical reaction equitation for the above neutralization.(1 mrk)
(iii)Calculate the molarity and normality of the H2SO4 solution.(2 mrks)
(iv)Calculate the molarity and normality of the NaOH solution.(3 mrks)
(v)Calculate the weight of NaOH per litre of solution.( 2 mrks)
(vi)Calculate the % purity of NaOH.(1 mrk)
[Relative atomic masses: H=1, S=32, O=16, Na =23]
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