Chemistry 401

Intermediate Inorganic Chemistry

University of Rhode Island

Exam 2

November 2, 2007
open notes, open book

1. Ionic compounds typically have high melting points because the lattice energy is so high. If one were to design an ionic compound with a melting point near room temperature, what properties would be required in the ions and in the lattice? Explain.

Answer

2. K+ has an ionic radius of 1.52 Å for coordination number 6 while Au+ has an ionic radius of 1.51 Å for coordination number 6. Which ion would you expect to be the stronger acid in an aqueous solution? Or would they have the same acid/base reactivity? Explain.

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3. FeO is typically nonstoichiometric, i.e. a more accurate representation of the chemical formula is FexO, where x ~ 0.95. A consequence of the nonstoichiometry is that FeO is a semiconductor. Is this a p-type or n-type semiconductor? Explain your reasoning.

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4. Which is the better base for boron trifluoride, methylamine or trimethylphosphine? Explain your reasoning.

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5. Consider the Latimer diagram for cobalt in acidic solution, given below. From this information, find the potential for the disproportionation of Co3+ at neutral pH. Assume that all cobalt ions are 0.1 M concentration.

CoO21.4Co3+1.92Co2+–0.282Co

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