Completed by Karen W. and Max L.
Name:_______________
Date:_____________
Ch. 8 & 9 Bonds & VSEPR
Test Key
80 points
Period:_________
AP chemistry
1. In regards to SeCl4 [20 points]
a. draw its Lewis structure
_
I Cl I
I
_
_
I Cl _
Se: - Cl I
_
I
I Cl I
_
b. sketch the molecule
Se 1 * 6 = 6
Cl 4 * 7 = 28
---34
-8
--26
c. what is/ are the bond angles in the molecule?
120° & 90°
d. what is the name of the shape of the molecule?
seesaw
e. Is it a polar or nonpolar compound? Justify your answer.
polar because the dipole moment is not equal to zero
2. Describe sigma- and pi- bonds; include and define the term, internuclear axis, in your answer
[15 points]
internuclear axis : connects nuclei of adjacent atoms involved in bond
Sigma bonds- overlap of AO/HO on the internuclear axis
Pi bonds- overlap of AO/HO that is not on the internuclear axis
3. In regards to CIF3, use valence bond theory to describe the bonds in the molecule; account
for all features on the central atom. If the hybrid orbitals are involved, then describe its formation
from the atomic orbitals & justify why it is needed [15 points]
i)
F
I
F - Cl - F
::
Cl 1 * 7 = 7
F 3 * 7 = 21
--28
-6
----22
-18
----4
Bond angle 90 ;
Sp3d b/c 5 shells
ii) Cl : [ ]
excite
-3s
--
Cl: [ ]
-3s
-- -3p
-- - 3p
3d
hybridize
Cl:
-- -- - - sp3d
iii ) overlap sp3d HO in Cl & 2p AO in F- x 3
iv) no HO; insufficient # e- to form 3 bonds in Cl
4. In regards to carbon dioxide. [15 points]
a. Draw all Lewis structure(s)
_
_
[ I O-C OI ]
[ I O C OI ]
[ IO
_
C
_
OI]
b. Determine the formal charges on all atoms in the preceding Lewis structures.
_
_
_
_
[ I O-C OI ]
[ I O C OI ]
[ IO C OI]
-1
0 +1
+1
0 -1
0
0
0
c. Pick the “best” Lewis structure; justify your choice.
_
_
[ I O C O I ] because it has the lowest magnitude in formal charge
5. Old topic: In a Beer’s Law lab, the calibration curve has two curves corresponding to two
different wavelengths of light. [15 points]
a. Sketch and label this calibration curve
b. Based on this curve, select the best wavelength; justify/rationalize your choice
Wavelength 1 is the best wavelength because larger △abs for given △concentration
c. What is Beer’s law? define/describe; which term(s) depend(s) on the wavelength of
light?
-Absorption: abc
a: molar absorptivity b: path length
c: concentration
-Molar absorptivity (a) depends on the wavelength of light