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22 Chemistry of the Nonmetals Solutions to Exercises 22.69 Analyze/Plan. Use information on the descriptive chemistry of carbon given in Section 22.9 to complete and balance the equations. Solve. (a) 800°C 2HCN(g)+6H₂O(g) (b) NaHCO₃(s) + (c) 22.70 (a) 2Mg(s) + CO₂ (g) 2MgO(s) + C(s) (b) (c) + 22.71 Analyze/Plan. Follow the rules for assigning oxidation numbers in Section 4.4 and the logic in Sample Exercise 4.8. Solve. (a) (b) SiBr₄, +4 (c) +2 (d) (e) B₂O₃, +3 (f) +4 22.72 (a) SiO₂, +4 (b) GeCl₄, +4 (c) NaBH₄, +3 (d) SnCl₂, +2 (e) (f) BCl₃, +3 22.73 Analyze/Plan. Consider periodic trends within a family, particularly metallic character, as well as descriptive chemistry in Sections 22.9 and 22.10. Solve. (a) Tin; see Table 22.8. The filling of the 4f subshell at the beginning of the sixth row of the periodic table increases Z and Zeff for later elements. This causes the ionization energy of Pb to be greater than that of Sn. (b) Carbon, silicon, and germanium; these are the nonmetal and metalloids in group 4A. They form compounds ranging from XH₄ (-4) to XO₂ (+4). The metals tin and lead are not found in negative oxidation states. (c) Silicon; silicates are the main component of sand. 22.74 (a) carbon (b) lead (c) germanium 22.75 Analyze/Plan. Consider the structural chemistry of silicates discussed in Section 22.10 and shown in Figure 22.34. Solve. (a) Tetrahedral (b) Metasilicic acid will probably adopt the single-strand silicate chain structure shown in Figure 22.34(b). The empirical formula shows 3 o and 2 H atoms per Si atom. The chain has the same Si to o ratio as metasilicic acid. Furthermore, in the chain structure, there are two terminal (not bridging) o atoms on each Si. These can accommodate the 2 H atoms associated with each Si atom of the acid. The sheet structure does not fulfill these requirements. 22.76 Carbon forms carbonates rather than silicates to take advantage of its ability to form pi bonds. Because of its relatively compact 2p valence orbitals, carbon can engage in effective pi-type overlap and form multiple bonds with itself and other elements. 682