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1044 Chapter 18 | Representative Metals, Metalloids, and Nonmetals
38. Write a balanced equation for the reaction of elemental boron with each of the following (most of these reactions require high temperature):
(a) F2
(b) O2
(c) S
(d) Se
(e) Br2
39. Why is boron limited to a maximum coordination number of four in its compounds?
40. Write a formula for each of the following compounds:
(a) silicon dioxide
(b) silicon tetraiodide
(c) silane
(d) silicon carbide
(e) magnesium silicide
41. From the data given in Appendix I , determine the standard enthalpy change and the standard free energy change for each of the following reactions:
(a) (b) (c)
42. A hydride of silicon prepared by the reaction of Mg2Si with acid exerted a pressure of 306 torr at 26 °C in a bulb with a volume of 57.0 mL. If the mass of the hydride was 0.0861 g, what is its molecular mass? What is the molecular formula for the hydride?
43. Suppose you discovered a diamond completely encased in a silicate rock. How would you chemically free the diamond without harming it?
18.4 Structure and General Properties of the Nonmetals
44. Carbon forms a number of allotropes, two of which are graphite and diamond. Silicon has a diamond structure. Why is there no allotrope of silicon with a graphite structure?
45. Nitrogen in the atmosphere exists as very stable diatomic molecules. Why does phosphorus form less stable P4 molecules instead of P2 molecules?
46. Write balanced chemical equations for the reaction of the following acid anhydrides with water: (a) SO3
(b) N2O3
(c) Cl2O7
(d) P4O10
(e) NO2
47. Determine the oxidation number of each element in each of the following compounds: (a) HCN
(b) OF2
(c) AsCl3
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