VSEPR

LARRY COMPTON
CHEMISTRY 151
RIO SALADO COLLEGE
2 NOVEMBER 2012

VALENCE SHELL ELECTRON PAIR REPULSION THEORY

Purpose:

The purpose of this lab is to further our understanding of interactions between molecules. We have to draw Lewis structures during this lab. Describe single, double and triple bonds. We also must predict the structure of a molecule using the VSEPR theory.

Materials:

Balloons
Colored Pencils
Molecular Model Kit

Procedures:

Part 1

1. Blow up all of the balloons in the lab kit and tie them. 2. Blow the three blue ones up slightly larger than you do the five red balloons.

3. The blue balloons will represent the repulsive field created by an unbonded pair of electrons. This field is slightly larger than the repulsive field created by the bonded electron pairs, represented by the red balloons.

Part 2

1. Use the model kit to construct a model of the CH4 molecule. Use the color chart that comes with your kit.

2. Draw a sketch of the CH4 model once constructed.

3. Repeat steps 1 and 2 for H2O, H3O+ , HCl, NH3, Cl2, N2, PCl3, CH3OH, and CO2.

Data:
Molecular Formula
Un-bonded Pairs on Central Atom
Molecular Geometry
Polarity
CH4
2
Tetrahedral
Non-Polar
H2O
2
Bent
Polar
H3O+
1
Trigonal Pyramidal
Polar
HC1
0
Linear
Polar
NH3
1
Trigonal Pyramidal
Polar
Cl2
0
Trigonal Bi-Pyramidal
Non-Polar
N2
1
Bent
Non-Polar
PCl3
1
Trigonal Pyramidal
Polar
CH3OH
2
Tetrahedral
Polar
CO2
4
Linear
Non-Polar

Calculations:

None required for this lab.

Results:
There were multiple bonds observed using the model kit.

Discussion Questions:

1. Explain the difference in polarity between CO2 and SO2 based on their molecular shapes.

SO2 is bent with two dipoles of oxygen bonds. These bonds will not cancel out like in CO2. SO2 has a stronger dipole.

2. Describe the similarities between H3O+ and NH3.

References: Brown, Theodore (2009). Chemistry: The Central Science (11th ed.) Upper Saddle River: Pearson Prentice Hall