Name
Section
Rec TA
Side 1 of 2
Ch 1a, Problem Set Six
Due Friday, Nov. 6, 2015
at 4 PM in the Ch1a box
Problems one and four are designated (z) as “no collaboration” problems.
Recall that problem sets are worth 200 points from now on,
and you may not substitute your Quiz One score for these sets.
Important note regarding grading of structures: no credit will be given for structures lacking
lone pairs and/or formal charges, where applicable. For any structures that require
3-dimensional representation, wedges and dashed wedges must be included.
z
1. (48 Points, 8 Each) For each of the following molecules, draw a Lewis dot structure and
state its geometry (in words) using VSEPR. Also, make sure the geometry is clear from
your drawings. Show any significant resonance structures (never more than two nonequivalent structures on this part) and formal charges. Be sure to explicitly show all lone
pairs!
a. CO2
b. PF5
c. CO
d. PH3
e. HCP
f. IF3
2. (30 Points, 6 Each) For each of the following molecules, draw a Lewis dot structure and
then state its geometry (in words) using VSEPR. (When multiple central atoms are
present, indicate the geometry at each atom) Also, make sure the geometry is clear from
your drawings. Show any significant resonance structures (never more than two nonequivalent structures) and formal charges. Be sure to explicitly show all lone pairs!
a. BrF5
b. N2O
c. CH3CCH
d. H2NBH2
e. SF2O
3. (75 points, 15 each) Electrochemistry involves transferring electrons from one molecule
to another in solution. This often requires the production of ions. Give the Lewis dot
structures for the following ions with any appropriate resonance structures and formal
charges. Make sure the geometry is clear from your drawings. (No need to state the
geometry in words using VSEPR, unless you want to.) Follow the directions next to
each species. If there are equivalent structures for anything that you draw, include
“and ___ equivalent structures” next to the applicable structure.
a.
b.
c.
d.
e.
CF+ (explicitly draw all structures, if there are more than one)
PO43- (5 non-equivalent, but only the two “best” are required)
ClO4- (5 non-equivalent, but only the three “best” are required)
OH3+ (explicitly draw all structures, if there are more than one)
ClO2− (explicitly draw the two “best” structures)
Name
Section
Rec TA
z
Side 2 of 2
Ch 1a, Problem Set Six
Due Friday, Nov. 6, 2015
at 4 PM in the Ch1a box
4. (32 Points, 8 Each) For each of the following pairs of molecules, identify which
molecule has the larger bond angle and briefly justify your answer.
a.
b.
c.
d.
NH3 and NH4+
BCl3 and PCl3
OF2 and SF2
NF3 and NCl3 (there are two explanations that we will accept, but you only need to cite
one of them)
5. (15 points) In class, Prof. Lewis described the catalytic destruction of ozone in the
stratosphere that occurs by chlorine species by the following two reactions:
Cl + O3 ⎯⎯
→ ClO + O 2
ClO + O ⎯⎯
→ Cl + O2
–––––––––––––––––––––––––––––––––––––––––––––––––––––
Net: O + O3 ⎯⎯
→ O2 + O2
One important reaction that helps to slow the above cycle is:
ClO + NO 2 ⎯⎯
→ ClONO 2 ,
which converts two very reactive species into the relatively unreactive molecule,
ClONO2.
a. (11 points) Draw the Lewis structures of ClO, NO2, and ClONO2, including any
significant resonance structures. (Don’t provide an exhaustive list of resonance
structures.)
b. (4 points) Use these Lewis structures to explain why ClO and NO2 are so much
more reactive than ClONO2. (Hint: There’s a better answer than resonance…)