C10J - Structure and Bonding
Problem Paper #2 (Week of Nov. 19, 2001)

1.(a) List all symmetry elements of cis- and trans- H(CH3)C=CH(CH3)
(b). What is the molecular geometry of XeOF4? List all its symmetry elements.

2.(a) Sketch the MO energy diagram for the hydrogen fluoride molecule. Draw the resulting bonding and antibonding MOs formed using boundary diagrams.
(b) Determine if this is consistent with the Lewis representation of the molecule.

3. On the basis of MO theory, explain what effect each of the following has on the properties of B2.
(i) B2 + e- ¾¾® B2-
(ii) B2 - e- ¾¾® B2+

4. Calculate the limiting radius, r+/r-, ratio for an AB3 ionic compound, which shows perfect packing of the ions.

5. Consider a 2-dimensional array of alternating cations and anions. If each ion is situated a distance r from each other, calculate to 3 significant figures, a value for the Madelung constant, M.

6.        Use the data below to calculate the lattice energy for MgCl2.

        DHatm Mg(s) = 147.7 kJ/mol;         DHion Mg(g) = 737.7 kJ/mol
        DHion Mg+ (g) = 1450.6 kJ/mol;     DHdiss Cl2(g) = 243.4 kJ/mol
        DHEA Cl(g) = -348.7 kJ/mol;         DHf MgCl2(s) = -644 kJ/mol
Answers to Problem Paper #2
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