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Date____________________
Chapter 8 Even Problems
40. Which compound in each of the following pairs of ionic substances has the most exothermic
lattice energy? Justify your answers.
a. LiF, CsF
LiF: smaller r
b. NaBr, NaI
NaBr: smaller r
c. BaCl2, BaO
BaO: bigger charges, smaller r
d. Na2SO4, CaSO4
CaSO4: bigger charges
e. KF, K2O
K2O: bigger charges
f. Li2O, Na2S
Li2O: smaller r
52. Estimate H for the following reaction using bond energies.
O
C2H4 + O3 → H3C–C–H + O2
H = C=C + 4 C–H + O=O + O–O – 4C–H – C–C – C=O – O=O
H = 614 + 4(413) + 495 + 146 – 4(413) – 347 – 745 – 495 = –332 kJ
64. Write Lewis structures that obey the octet rule for each of the following molecules and ions.
a. SO42–, PO43–, ClO4–
all tetrahedral
b. SO32–, PO33–, ClO3–
all trigonal pyramidal
c. ClO2–, SCl2, PCl2–
all bent
d. Considering your answers to parts a, b, and c, what conclusions can you draw concerning
structures containing the same number of atoms and the same number of valence electrons?
They have the same molecular shape.
68. Some of the important pollutants in the atmosphere are ozone (O3), sulfur dioxide, and sulfur
trioxide. Write Lewis structures that obey the octet rule for these three molecules. Show all
resonance structures where applicable.
O=O–O
↔
O–O=O
O=S–O
↔
O–S=O
O
O–S–O
O
↔
O=S–O
O
↔
O–S=O
92. Write Lewis structures and predict whether each of the following is polar or nonpolar.
a. HOCN (exists as HO–CN)
polar
b. COS (C is central atom)
polar
c. CO2
d. CF2Cl2
polar
e. SeF6
nonpolar
f. H2CO (C is the central atom)
nonpolar
polar
94. Write a Lewis structure and predict the molecular structure and polarity for each of the
following sulfur fluorides: SF2, SF4, SF6, and S2F4 (exists as F3S–SF). Predict the F–S–F bond
angles in each molecule.
SF2: bent, polar, 104.5º
SF4: see-saw, polar, 90/120/180º
SF6: octahedral, nonpolar, 90º
S2F4: see-saw / bent, polar, 90/180º