Chapter 3 Homework Solutions 4. (a) Molecular formula of pyruvic acid is C3H4O3.(b) Molecular formula of isocitric acid is C6H8O7. 12. 18 gal×3790 mL1 gal×1 cm31 mL×0.692 g1 cm3=4.7×104g4.7×104g×1 lb453.59 g=1.0×102lb14. (a) Benzene Molecular Formula: C6H6(b) Vitamin C Molecular Formula: C6H8O620. A general rule for the charge on a metal cation: the group number represents the number of electrons lost. Hence, the group number will be the cation’s positive charge. (a) Lithium (Group 1A) Li+(b) Strontium (Group 2A) Sr2+(c) Aluminum (Group 3A) Al3+(d) Calcium (Group 2A) Ca2+(e) Zinc (Group 2B) Zn2+21. For nonmetal elements in Groups 5A-7A, the electrons gained by an atom to form a stable anion are calculated using the formula: 8 – (group number). That means the (group number) – 8 is the negative charge of the anion. (a) nitrogen (Group 5A) 5 – 8 = –3 N3–(b) sulfur (Group 6A) 6 – 8 = –2 S2–(c) chlorine (Group 7A) 7 – 8 = –1 Cl–(d) iodine (Group 7A) 7 – 8 = –1 I–(e) phosphorus (Group 5A) 5 – 8 = –3 P3–22. Barium (Group 2A) has a +2 charge. Bromine (Group 7A) has a –1 charge. So, the ions are Ba2+and Br–. 24. (a) selenium (Group 6A) 6 – 8 = –2 Se2–(b) fluorine (Group 7A) 7 – 8 = –1 F–(c) nickel (a transition metal) Ni2+(d) nitrogen (Group 5A) 5 – 8 = –3 N3–27. (a) Aluminum ion (from Group 3A) is Al3+. Chloride ion (from Group 7A) is Cl–. AlCl is nota neutral combination of these two ions. The proper formula would be AlCl3. [net charge = +3 + 3 ×(–1) = 0 ] (b) Sodium ion (Group 1A) is Na+. Fluoride ion (from Group 7A) is F–. NaF2is nota neutral combination of these two ions. The proper formula would be NaF. [net
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