Chemistry 401

Intermediate Inorganic Chemistry

University of Rhode Island

Exam 2

November 5, 2010
open book, open notes

1. Which of the following schemes for the repeating pattern of close-packed planes are not ways of generating close-packed lattices? (a) ABCABC ... (b) ABAC ... (c) ABBA ... (d) ABCBC ... (e) ABABC... (f) ABCCB ... Explain.

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2. The Coulombic attraction of nearest-neighbor cations and anions accounts for the bulk of the lattice enthalpy of an ionic compound. With this fact in mind, estimate the order of increasing lattice enthalpy of (a) MgO, (b) NaCl, (c) AlN, all of which crystallize in the rock-salt structure. Give your reasoning.

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3. Predict whether the equilibrium constants for the following reactions should be greater than 1 or less than 1. Explain.

a) CdI2(s) + CaF2(s) CdF2(s) + CaI2(s)

b) [CuI4]2–(aq) + [CuCl4]3–(aq) [CuCl4]2–(aq) + [CuI4]3–(aq)

c) NH2(aq) + H2O(l) NH3(aq) + OH(aq)

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4. Balance the following redox reaction in acid solution: MnO4(aq) + H2SO3(aq) → Mn2+(aq) + HSO4(aq). Predict the qualitative pH dependence on the net potential for this reaction (i.e. increases, decreases, remains the same).

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5. Draw a Frost diagram for mercury in acid solution. Comment on the tendency of any of the species to act as an oxidizing agent, a reducing agent, or to undergo disproportionation.

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6. Calculate the lattice energy (in units of kJ/mol) for ZnO in the wurtzite structure using the Born-Landé equation and using a Born-Haber cycle. Compare the two answers and comment on any differences. Useful data: the Born exponent, n, = 8; the sublimation energy of zinc = 130.4 kJ/mol; and the standard heat of formation of zinc(II) oxide = –350.5 kJ/mol. Other data can be found in the textbook.

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