CHEM 111 University of San Francisco Chemistry Questions

CHEM 111Homework – Ch. 8
due in class Fri 11/11
Name _______________________________________
Questions are worth 4 points each.
1. For each of the following compounds: (a) draw a full Lewis structure; (b) indicate the shape of the
molecule and the bond angle around the central atom; and (c) indicate whether or not the molecule is
polar.
a. COS (C is in the middle)
b. PH3
2. For each of the following compounds: (a) draw a full Lewis structure; (b) indicate the shape of the
molecule and the bond angle around the central atom; and (c) indicate whether or not the molecule is
polar.
a. SbF4–
b. SO32–
3. Nitrosyl fluoride (NOF) has an atom sequence in which all atoms have formal charges of zero. Draw
a Lewis structure consistent with this fact.
4. Hydrogen cyanide (and organic nitrile, which contain the cyano group) can be catalytically reduced
with hydrogen to form amines. Draw a Lewis structure for each component of the reaction below, and
use bond energies to determine the enthalpy of reaction, DrH°.
HCN (g) + 2 H2 (g) ® CH3NH2 (g)
5. (Challenge question) Dinitrogen monoxide (N2O), used as the anesthetic “laughing gas” in dental
surgery, supports combustion in a manner similar to oxygen, whit the nitrogen atoms forming N2.
Draw three resonance structures for N2O (one N is central), and use formal charges to decide the
relative importance of each. What correlation can you suggest between the most important structure
and the observation that N2O supports combustion?