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Sch2101:Chemical Bonding And Structure Question Paper
Sch2101:Chemical Bonding And Structure
Course:Bachelor Of Crop Protection
Institution: Meru University Of Science And Technology question papers
Exam Year:2013
QUESTION ONE (30 MARKS)
a) Explain the formation of a chemical bond (4 Marks) b) Write Lewis dot symbols for atoms of the following elements: i. N ii. S2- (4 Marks)
c) Draw the Lewis structures for the following molecules and ions. i. SiCI4 ii. HCOOH iii. CO32-
(6 Marks)
d) Define octet rule. Write its significance and limitations.
(8 Marks)
e) Write the favourable factors for the formation of ionic bond.
(4 Marks)
f) Discuss the shape of the following molecules using VSEPR model:
(4 Marks)
i. BeCl2 ii. AsF5
QUESTION TWO (20 MARKS)
a) Elements X, Y, Z have atomic numbers 6, 9 and 12 respectively. Which one;
i. Forms anion ii. Forms cation
2
iii. Has 4 electrons the outermost orbit.
(6 Marks)
b) Covalent compounds are usually liquids or gases. Explain.
(4 Marks)
c) Although geometries of NH3 and H2O molecules are distorted tetrahedral, bond angle in water is less than that of ammonia. Discuss. (4 Marks)
d) Write the significance / applications of dipole moment.
(6 Marks)
QUESTION THREE (20 MARKS)
a) Explain with the help of suitable example, polar covalent bond.
(5 Marks)
b) Which out of NH3 and NF3 has a higher dipole moment and why?
(4 Marks) c) With the aid of a diagram, clearly illustrate the relationship between the potential energy versus oppositely charged particles. (5 Marks) d) (i) Define the bond length. (2 Marks) (ii) How do you express the bond strength in terms of bond order? (4 Marks)
QUESTION FOUR (20 MARKS) a) Define Lattice Energy
(2 Marks)
Order the following ionic compounds in order of increasing magnitude of lattice energy. CaO, KBr, KC1, SrO (4Marks)
b) The partially completed Bohr-Haber cycle for rubidium chloride is shown below
(2 Marks)
3
i. Complete the empty boxes. (2 Marks)
ii. Using the data below, calculate the enthalpy of formation for rubidium chloride.
(4 Marks)
kJmol-1
First ionisation energy of rubidium +403
Enthalpy of atomisation of rubidium +81
Bond enthalpy of chlorine (C12) +242
Electron affinity of chlorine -348
Lattice enthalpy of rubidium chloride +685
c) i) Distinguish between a sigma and pi bond. (4 Marks)
ii) Explain the formation of H2 molecule on the basis of valence bond theory. (4 Marks)
QUESTION FIVE (20 MARKS)
a) Name the following polyatomic ions
i. IO4-
ii. ClO3- (4 Marks)
b) Draw electron dot diagram to depict the formation of;
i. Magnesium oxide from 12 24 and, 8 16 (4 Marks)
c) Four atoms are arbitrarily labeled D, E, F, and G. Their electronegativities are as follows: D =3.8, E =3.3, F =2.8, and G =1.3. If the atoms of these elements form the molecules DE, DG, EG, and DF, how would you arrange these molecules in order of increasing covalent bond character? (4 Marks)
d) Write the resonance structures for (i)NO2 and (ii) NO3-. (4 Marks)
e) Define electronegativity. How does it differ from electron gain enthalpy? (4 Marks)
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