CHEM 114, Fall 2014
Lab Practical No. 3
Name:____________________________________________
1. For each of the following give 1) the most appropriate Lewis structure, 2) all resonance structures,
and 3) formal charges for all atoms having any.
a) CO 32−
b) OCN − . Explain which structure(s) are important and why.
2. Circle the following molecules which have a dipole moment
a) NF3
b) CH2Br2
c) CBr4
d) COS
e) OF2
f) AlCl3
g) PH3
h) Cl2O
i) ICl2
j) H2S
3. PBr2F3 does not have a dipole moment.
a) Use VSEPR to predict and carefully draw the structure consistent with this data.
b) Why does this structure have no dipole moment? Explain your answer
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4. For each of the following give a) the electronic geometry (electron group arrangement) for the central
atom, b) the molecular geometry (shape), c) all bond angles (when distorted, state whether the angle is
greater than or less VSEPR prediction and give the prediction), and d) draw the best three-dimensional
structure (omit resonance structures and omit drawing lone pairs of electrons on outer atoms but
include them on the central atom.)
Formula
Electronic geometry
Molecular geometry
Distortion
Structure
ClF3
XeCl2
SnCl 3−
I 3−
SeCl6
XeOF4
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4. For each of the following compounds, 1) give the hybridization of all atoms, and 2), if present, circle
the portion of any molecule that is conjugated.
H
H
S
O
H
O
C
H
N
C
O
C
H
C
C
H
H
H
C
O
H
F
N
C
C
N
F
Br
F
5. The diatomic molecule OH exists in the gas phase and it plays an important part in combustion
reactions and is a reactive oxidizing agent in polluted air. The bond length and bond energy are
measured to be 97.06 pm and 424.7 kJ/mol respectively. The OH molecule is analogous to the HF
molecule and that the MOs result from the overlap of a pz orbital from oxygen and the 1s orbital of H
and the O-H bond lies along the z-axis.
a) Draw pictures of the sigma bonding and antibonding molecular orbitals in OH.
b) Which of the two MOs have the greater hydrogen 1s character?
c) Can the 2px orbital of O form MOs with the 1s orbital of H? Explain.
d) Knowing that only the 2p orbitals of oxygen interact significantly with the 1s orbital of H complete the
MO energy-level diagram for OH
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e) Estimate the bond order for OH.
f) Predict whether the bond order for OH+ is greater than, less than, or the same as that of OH. Explain.
6. Consider the compound CH2CHCHCH2 with the four carbon atoms forming a chain.
a) Determine the number of valence electrons.
b) Draw the Lewis structure.
c) Give the hybridization of each carbon atom.
d) Which bonds are σ bonds?
e) How many σ electrons are there?
f) How many π electrons are there?
g) ) Each π electron is initially in an unhybridized carbon p orbital. How many π molecular
orbitals can be made?
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h) Draw the π molecular orbitals, ordered according to energy, clearly showing all nodes. Label
the MO’s as bonding, antibonding, nonbonding (all need not apply).
i) Draw the π electron molecular orbital energy level diagram, fill with the π electrons, and
indicate the HOMO and LUMO energies. Is this compound diamagnetic or paramagnetic? Why?
7. a) Give the ground state electron configuration of a nitrogen atom.
b) Give the ground state electron configuration of a carbon atom.
c) Draw the Lewis structure for CNd) Draw the molecular orbital (MO) energy level (correlation) diagram for the valence electrons of CN- .
(Note: Your diagram must be NEAT, labeled completely, and illustrate relative energies of the atomic
and molecular orbitals.)
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e) Fill in the table
Species No. of valence eCN+
CNCN
Electronic Structure
Paramagnetic (y/n)
Stable (y/n)
Bond Order
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