10.2: LAB 10 B - MOLECULAR GEOMETRIES - MODELING KIT
- Page ID
- 528393
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)The purpose of this experiment is to:
- Use the concepts of Lewis structures and VSEPR to predict molecular geometry.
- Create 3D models of representative molecules and compare the shapes with predictions.
- Use the 3D models to help predict whether the molecule will be polar or nonpolar.
INTRODUCTION
A molecule’s 3-dimensional structure is one of the key predictors of its physical and chemical properties. One important property is its polarity. Most covalent bonds are polar; however, the overall polarity of a molecule depends on its 3D geometry. When given a drawing of a molecule, visualizing its 3D structure can be challenging, making predictions about its polarity difficult. The 3D structure can be more easily evaluated by building models with a modeling kit or using a small 3D model, such as one created by a 3D printer.
Follow all your instructor’s instructions to effectively use your model kit or 3-D printer, and return all the models and equipment as instructed.
EQUIPMENT* NEEDED
- Model kit / 3-D printer (if using a 3-D printer, please see the other procedure)
- A combination of both can also be used. Students can use the model kits to complete the data while their 3-D models are being printed.
* Images of equipment needed in this lab can be found in the appendix (the equipment may differ a little or be subject to changes; follow your instructors’ directions).
EXPERIMENTAL PROCEDURE
- Draw the Lewis structures and use VSEPR theory to predict molecular geometry and whether the molecule will be polar or nonpolar.
- Create 3D models of the molecules (using a Modeling Kit or 3D printer; if using a 3D printer, please see the other procedure for printing the models).
- Compare the shapes and use the 3D models to help determine if the molecule will be polar or nonpolar.
Create models of the molecules listed in the data table using the modeling kit provided by your instructor. Include the image in the data table or upload them separately, ensuring they are labeled correctly if uploaded separately.
PRE-LAB QUESTIONS
Name: _________________________________
- Describe the similarities and differences between ionic bonds, polar covalent bonds, and pure covalent bonds.
- Explain in your own words how it can be determined if a molecule containing polar bonds is polar or nonpolar.
- Draw the Lewis structure of a molecule of each of the compounds in the Data Table and use Valence Shell Electron-Pair Repulsion (VSEPR) theory to predict the molecule’s geometry. Fill in the appropriate spaces on the table with your answers.
DATA AND OBSERVATIONS
Name: _________________________Lab Partner(s): ______________________________
|
Molecule |
CO2 |
|
|---|---|---|
|
# valence electrons |
|
Lewis Structure |
|
# of electron domains |
|
|
|
Electron domain geometry |
|
|
|
# of lone pairs |
|
Image of the Model |
|
Molecular geometry |
|
|
|
Polar or Nonpolar? |
|
|
Molecule |
H2CO |
|
|---|---|---|
|
# valence electrons |
|
Lewis Structure |
|
# of electron domains |
|
|
|
Electron domain geometry |
|
|
|
# of lone pairs |
|
Image of the Model |
|
Molecular geometry |
|
|
|
Polar or nonpolar? |
|
|
Molecule |
SO2 |
|
|---|---|---|
|
# valence electrons |
|
Lewis Structure |
|
# of electron domains |
|
|
|
Electron domain geometry |
|
|
|
# of lone pairs |
|
Image of the Model |
|
Molecular geometry |
|
|
|
Polar or nonpolar? |
|
|
Molecule |
CF4 |
|
|---|---|---|
|
# valence electrons |
|
Lewis Structure |
|
# of electron domains |
|
|
|
Electron domain geometry |
|
|
|
# of lone pairs |
|
Image of the Model |
|
Molecular geometry |
|
|
|
Polar or nonpolar? |
|
|
Molecule |
NH3 |
|
|---|---|---|
|
# valence electrons |
|
Lewis Structure |
|
# of electron domains |
|
|
|
Electron domain geometry |
|
|
|
# of lone pairs |
|
Image of the Model |
|
Molecular geometry |
|
|
|
Polar or nonpolar? |
|
|
Molecule |
H2O |
|
|---|---|---|
|
# valence electrons |
|
Lewis Structure |
|
# of electron domains |
|
|
|
Electron domain geometry |
|
|
|
# of lone pairs |
|
Image of the Model |
|
Molecular geometry |
|
|
|
Polar or nonpolar? |
|
|
Molecule |
BF3 |
|
|---|---|---|
|
# valence electrons |
|
Lewis Structure |
|
# of electron domains |
|
|
|
Electron domain geometry |
|
|
|
# of lone pairs |
|
Image of the Model |
|
Molecular geometry |
|
|
|
Polar or nonpolar? |
|
|
Molecule |
PCl5 |
|
|---|---|---|
|
# valence electrons |
|
Lewis Structure |
|
# of electron domains |
|
|
|
Electron domain geometry |
|
|
|
# of lone pairs |
|
Image of the Model |
|
Molecular geometry |
|
|
|
Polar or nonpolar? |
|
|
Molecule |
IF5 |
|
|---|---|---|
|
# valence electrons |
|
Lewis Structure |
|
# of electron domains |
|
|
|
Electron domain geometry |
|
|
|
# of lone pairs |
|
Image of the Model |
|
Molecular geometry |
|
|
|
Polar or nonpolar? |
|
POST-LAB QUESTIONS
- How does the 3D model help you to determine if a molecule is polar or nonpolar?
- Is the 3D model different from what you expected in any way? If so, how?
- What are the advantages and disadvantages of a 3D model vs. looking at the model on a computer screen?
Please click here to access the Pre-Lab, Data Tables, and Post-Lab in Word or PDF format. Complete them and upload according to your instructor's instructions.