Chem 6A Quiz 4_key_Sect_E09_E04_E05

Chem 6A Quiz 4_key_Sect_E09_E04_E05 -...

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Unformatted text preview: QUIZ
4
E09/E04/E05
 Section
E____
 
 
 NAME
(Last,
First):
_______KEY___________________
 Your
signature:
_____________________________
 Chemistry
6A
Fall
2008
 UCSD
PID:
|A|__|__|__|__|__|__|__|__|
 Total
Points:
_______
/
20
 
 
 
 You
have
10
minutes
to
complete
this
quiz.
Please
show
all
your
work,
but
write
the
 answers
in
the
designated
spaces.
The
points
allotted
for
each
question
are
indicated
in
 parenthesis.
 
 Potentially
Helpful
Constants:

 Potentially
Helpful
Equations:
 
 
 ‐31
kg
 Mass
of
electron,
me
=
9.10938
x
10 EK
=
½mv2
 Mass
of
proton,
mp
=
1.67262
x
10‐27
kg
 







 Mass
of
neutron,
mn
=
1.67493
x
10‐27
kg
 
 Fundamental
charge,
e
=
1.60218
x
10‐19
C
 c
=
νλ
 g
=
9.80665
m•s‐2
 8
m•s‐1
 E=
hν
 c
=
2.99792
x
10 λparticle
=
h(v)
 h
=
6.62608
x
10‐34
J•s
 Etot
=
Ek
+
EФ
 
 =
(1( 1))2−
1( 2))2)
 
 
 Potentially
Helpful
Conversion
Factors:
 1
J
=
1
N•m
 1
N
=
1
kg
m
s‐2
 1
L
=
103
cm3
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1) To
construct
the
molecular
shape
from
a
particular
Lewis
structure,
chemists
 employ
the
VSEPR
model.


Draw
the
Lewis
structure
of
two
of
the
following
 molecules
and
apply
VSEPR
theory
to
answer
the
following
(8pts):
 Molecule
 Lewis
 Octet
Rule
 AXnEm
‐ Molecular
 Structure
 Violated?
 Designation
 Geometry
 (Yes/No)
 
 
 
 
 
 ICl3
 Yes
 AX3E2
 T‐shaped
 
 
 
 
 
 
 XeF4
 Yes
 AX4E2
 Square
Planar
 
 
 
 
 
 
 
 
 
 +
 PCl4 No
 AX4
 Tetrahedral
 
 
 
 
 2)
In
general,
as
bond
order
_INCREASES_(increases,
decreases),
the
bond
length
 decreases
and
the
bond
dissociation
energy
_INCREASES_(increases,
decreases).
(2pts)
 
 3)
What
is
the
difference
between
electronegativity
and
electron
affinity?
2
pts.
 
 Electronegativity
is
the
ability
of
an
atom
to
attract
electrons
to
itself
when
it
is
a
 part
of
a
compound
(Atkins/Jones).

Electron
affinity
is
the
energy
released
when
an
 electron
is
added
to
a
gas‐phase
atom
or
monatomic
ion
(Atkins/Jones).

Electronegativity
 is
a
more
abstract
value
since
each
atom
is
compared
to
Fluorine
(the
most
 electronegative
atom)
while
electron
affinity
supplies
an
energy
value.




 
 4)
There are 3 Lewis structures for OCN-. Please complete these structures by drawing the correct number of electrons for each atom and the correct number of bonds between atoms, if necessary. Assign Formal Charges to each atom and circle the most important form. (8 pts.) 
 

 FCN
=
5‐(2+(½)(6))
=

0
 FCN
=
5‐(6+
(½)(2))
=
‐
2
 FCN
=
5‐(4+(½)(4))
=
‐1
 
 FCC
=
4‐(0+(½)(8))
=


0
 FCC
=
4‐(0+
(½)(8))
=



0
 FCC
=
4‐(0+(½)(8))
=


0
 
 FCO
=
6‐(6+(½)(2))
=
‐1
 FCO
=
6‐(2+
(½)(6))
=
+1
 FCO
=
6‐(6+(½)(2))
=


0
 
 
 
 
 Formal
Charge
=
#
valence
e‐
‐(#lone
e‐
+
½
#
bonding
e‐)
 Total
Valence
#
Electrons=
5Nitrogen
+
4Carbon+
6Oxygen
+
1ion
 (‐1)
Charge
is
shared
relatively
equally
by
the
Oxygen
atom
and
the
Nitrogen
atom.
 ...
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