Ch 9 Homework
32. Which compound has the most negative energy of ion pair formation? Which has the least
negative value? (a) NaCl
(b) MgS
(c) MgF 2
34. Place the following compounds in order of increasing lattice energy (from least negative to
most negative): LiI, LiF, CaO, RbI.
37. Which compound in each of the following pairs should require the higher temperature to
melt? (See Study Question 36.)
(a) NaCI or RbCI
(b) BaO or MgO
(c) NaCI or MgS
39. Draw Lewis structures for the following molecules or ions:
(a) CS2
(b) NO2(c) BF 4-
(d) Cl2SO
41. Draw Lewis structures for each of the following molecules:
(a) Methanol, CH30H (C is the central atom)
(b) Vinyl chloride, H2C = CHCI, the molecule from which PVC plastics are made. Its
structure resembles that of C2F4 in Study Question 40.
(c) Acrylonitrile, H2C= CHCN, the molecule from which materials such as Orlan are
made
42. Show all possible resonance structures for each of the following molecules or ions:
(a) S02
(b) N02 (c) SCN45. Draw Lewis structures for each of the following molecules or ions:
(a) BrF5
(b) IF3
(c)IBr2
(d) BrF2 +
46. Determine the formal charge on each atom in each of the following molecules or ions:
(a) N2H4
(b) P04 3(c) BH4 (d) NH20H
48. Determine the formal charge on each atom in the following molecules and ions:
(a) N02 +
(b) N02 (c) NF3
(d) HN03
51. For each pair of bonds, indicate the more polar bond and use an arrow to show the direction
of polarity in each bond.
(a) C-O and C-N
(b) P-Br andP-CI
(c) B-O and B-S
(d) B-F andB-I
53. Urea, (NH2)2CO, is used in plastics and fertilizers. It is also the primary nitrogen-containing
substance excreted by humans. Draw the molecule with C=O as the center
(a) Which bonds in the molecule are polar and which are nonpolar?
(b) Which is the most polar bond in the molecule? Which atom is the negative end of the bond
dipole?
54. Considering both formal charges and bond polarities, predict on which atom or atoms the
negative charge resides in the following anions:
(a) BF4 (b) BH4 (c) OH(d) CH3C0257. Compare the electron dot structures of the carbonate (C03 2- ) and borate (B03 3- ) ions.
(a) Are these ions isoelectronic?
Ch 9 Homework
pg
1
(b) How many resonance structures does each ion have?
(c) What are the formal atom charges in each ion?
(d) If an H+ ion attaches to C03 2- to form the bicarbonate ion, HC03 -,
does it attach to an 0 atom or to the C atom?
61. Specify the number of bonds for each of the following molecules or ions.
Give the bond order for each bond.
(a) CN(b) CH3CN (c) S03
(d) CH3CH=CH2
64. Consider the nitrogen-oxygen bond lengths in N02 +, N02 -, and N03 -. In which ion is the
bond predicted to be longest? Which is predicted to be the shortest? Explain briefly.
69. Phosgene, Cl2CO, is a highly toxic gas that was used as a weapon in World War I. Using the
bond energies of Table 9.9, estimate the enthalpy change for the reaction of carbon monoxide
and chlorine to produce phosgene. (Hint: First draw the electron dot structures of the reactants
and products so you know the types of bonds involved.)
CO(g) + Cl2(g) -> Cl2CO(g)
74. The following molecules or ions all have two oxygen atoms attached to a central atom. Draw
the Lewis structure for each one and then describe the electron-pair geometry and the molecular
geometry. Comment on similarities and differences in the series.
(a) CO2
(b) N02 (c) 03
(d) CI02 75. The following molecules or ions all have three oxygen atoms attached to a central atom.
molecular geometry. Comment on similarities and differences in the series.
(a) C03 2(b) N03 (c) S03 2(d) CI03 78. Give approximate values for the indicated bond angles.
(a) O-S-O in S02
(b) F-B-F angle in BF3
(c) Cl- C - Cl angle in Cl2CO
(d) H -C- H (angle 1) and C-C=N (angle 2) in acetonitrile CH3CN
83. Consider the following molecules:
(a) CH4
(b) NCl3
(c) BF3
(d) CS2
(i) Which compound has bonds with the greatest degree of polarity?
(ii) Which compounds in the list are not polar?
85. Which of the following molecules is (are) polar? For each polar molecule indicate the
direction of polarity, that is, which is the negative and which is the positive end of the molecule.
(a) BeCl2
Ch 9 Homework
(b) HBF2
(c) CH3Cl
(d) S03
pg
2
Ch 9 Homework
pg
3