Chemistry 401

Intermediate Inorganic Chemistry

University of Rhode Island

Exam 2

November 6, 2009
open book, open notes

1. MgO is found in the rock salt (NaCl) structure with a lattice constant of 421.2 pm. Is this consistent with the ionic radii given in the textbook? Explain.

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2. The band gap in MgO is 7.8 eV. Is MgO likely to be an effective semiconductor? Why or why not? What could you dope MgO with to form a p-type semiconductor? An n-type semiconductor? Explain your reasoning in each case.

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3. In terms of Brønsted-Lowry theory, do you expect MgO to be an acid, a base, or a neutral compound? Explain.

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4. Predict if the following reactions occur. If reaction does occur, balance the reaction.

a. MgO(s) + HF(aq)

b. MgO(s) + H2S(aq)

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5. MgO can be formed by dehydration of Mg(OH)2. Using data from Latimer Diagrams and a Born-Haber (or thermochemical) cycle, find ΔG° for the dehydration reaction of Mg(OH)2. ΔGf° for MgO is –569.4 kJ/mol (this is for the formation of MgO from the elements). ΔG° = –nFE°.

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