CHEM 150
Assignment #2
(Due Oct. 17th, in-class)
Answer each of the following questions, showing all of your work.
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1) Draw Lewis structures for each of the following molecules/polyatomic ions. Indicate the VSEPR molecular
geometry in each case.
a. PCl3
b. ClO2c. CO
a
b
trigonal pyramid
angular (or bent)
c
linear
2) Arrange the following two-atom bonds in order of increasing polarity (lowest polarity  highest polarity).
B-F, C-P, S-O
Answer: determine the bond polarity order by the difference in the electronegativity for the two elements in
each bond.
C-P < S-O < B-F
3) Which of the following molecules/polyatomic ions are polar? (Answers highlighted)
a. PCl3
b. NH4+
c. ClO2d. I2
e. CO32f. H2CO
4) Indicate the formula weights for each of the following substances:
a. Sodium nitrate: NaNO3 : 22.99g/mol Na + 14.01 g/mol N + 3 x 16.00 g/mol O = 85.00 g/mol
b. K2CO3: 2 x 39.10 g/mol K + 12.01 g/mol C + 3 x 16.00 g/mol O = 138.21 g/mol
c. Br2: 2 x 79.90 g/mol Br = 159.80 g/mol
5) Complete the Lewis structure for the amino acid shown below. What are the local molecular geometries
around the atoms indicated? (i.e. a and b)
H
H
H
O
N
C
C
O
H
a)
b)
Answer:
Local molecular geometries:
a) Trigonal pyramid
b) Trigonal planar
H