molecular geometry assignment quizlet

Molecular Geometry & VSEPR Quiz

This online quiz is intended to give you extra practice in identifying the molecular and electron geometry of chemical compounds using VSEPR theory.

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Molecular Geometry

You will want to familiarize yourself with chapter 10, "The Shapes of Molecules", in your text, Chemistry: The Molecular Nature of Matter and Change , 3 rd edition by Martin Silberberg, before beginning this lab. By following the link, you can read through a summary of chapter 10 (it may take a minute for all the graphics to download) that gives the steps for drawing molecules and predicting their shapes.

About the Assignment

To complete this lab assignment, you will be accessing a website that requires the CHIME plug-in. The plug-in is available on the school computers; however, you will probably need to install it on your home computer. If you can see the structure below, the plug-in has been correctly installed.

Getting the Plug-In:

Using an ITAP computer on campus

Using your home computer

Using the Plug-In :

Get used to the CHIME plug-in

NOTICE by looking at the 3D model simulations, you can see the name for the molecular geometry comes from the shape of the compound when the lone pairs on the central atom are ignored.

For Example:

You should familiarize yourself with the different shapes (and the corresponding names) that result from replacing outer atoms with lone pairs.

Practice Problems:

Check your understanding with a few practice problems. The practice problems are intended for you to test yourself and see if you understand how to draw Lewis Dot Structures and predict molecular geometries. These problems are for you alone and will not be graded.

Molecular Geometry Lab:

All parts of the assignment (Molecular Geometry Lab - Parts I, II(a), II(b) and III) are to be answered in your lab notebook. You should follow a specific format for entering your answers in your notebook.

You can access any part of the lab assignment with the following links.

• Contents >

Lab 5 - Molecular Geometry

• A To explore some simple molecular structures.
• B To explore the relationship between bond order and bond length.
• C To explore resonance structures.
• 1 To compare Lewis structures to three-dimensional models.
• 2 To visualize the three-dimensional structures of some common molecules.
• 3 To obtain bond angle, bond length, and hybridization data for molecules.
• 4 To rationalize differences in predicted and measured values.
• 5 To learn how to use molecular modeling software.

Introduction

• 1 Calculate the electrons required (ER) = the minimum number of electrons necessary to satisfy the octet rule for the non-hydrogen atoms and the duet rule for hydrogen. For CHO 2 - , this would be (2 electrons x 1 hydrogen atom) + (8 electrons x 3 non-hydrogen atoms) = 2 + 24 = 26 electrons required.
• 2 Calculate the number of available valence electrons (VE) = the total number of electrons available for the molecule. For example, in CHO 2 - , this would be (1 C atom x 4 electrons) + (1 H atom x 1 electron) + (2 O atoms x 6 electrons) + (1 electron as the ion has a charge of -1) = 4 + 1 + 12 + 1 = 18 valence electrons. NOTE: For ions, the charge must be factored into this calculation by adding the charge on an anion or subtracting the charge on a cation.
• 3 Calculate the Shared Pairs (SP) = the number of electrons to be shared in bonds. The SP is 1/2 (ER-VE); for CHO 2 - , this would be 1/2 (26 - 18) = 4 shared pairs or four bonds.
• 4 Calculate the Lone Pairs (LP) = the number of electron pairs belonging to only one atom. The LP is 1/2 (VE-(2xSP)); for CHO 2 - , this would be 1/2(18 - (2x4)) = 5 lone pairs. Notice that VE = 2 x (SP + LP).
• 5 Place the first atom in the molecular formula as the central atom, surrounded by the other atoms in the compound.

• 6 Draw bonds (shared pairs) from the central atom to each surrounding atom. The bonds are represented as lines; each line represents two electrons. The number of lines should be equal to the number of shared pairs calculated in step 3, which in this case is four. Since hydrogen follows the duet rule, it prefers only one bond. The fourth bond can be drawn to either one of the oxygen atoms.

• 7 Draw lone pairs on each of the non-hydrogen atoms. A lone pair is represented as two dots; each dot represents an electron. Each non-hydrogen atom prefers eight electrons in the vicinity of the atom. If an atom has 1 bond, it requires 3 lone pairs. If an atom has 2 bonds, it requires 2 lone pairs. If an atom has 3 bonds, it requires 1 lone pair. If an atom has 4 bonds, do not add any additional lone pairs. In our example, C requires no lone pairs, one oxygen requires 3 lone pairs and one oxygen requires 2 lone pairs.

• 1 Chem-Tutor model kit
• 1 computer with internet browser
• 1 Molecular Geometry In-Lab assignment in WebAssign

About the model kit

About the computer modeling software, waste disposal, prior to class.

Lab Procedure

• Launch a web browser.
• Open one partner's Molecular Geometry In-Lab in WebAssign.

Part A: Exploring Simple Structures

• • Review the correct, complete Lewis structure(s), including any resonance structures and any formal charges that you drew in your Prelab assignment.
• • Build the molecule with the model set.
• • Look at the molecule in your In-Lab assignment on WebAssign.
• • Fill in the table and answer the questions below.

Part B: Bond Order vs Bond Length

Part c: resonance structures.

• • When you are done, clean up any model set structures and leave the sets as you found them when you arrived in the lab.
• • Before leaving, go to a computer in the laboratory and enter your results in the InLab assignment. If all results are scored as correct, log out. If not all results are correct, try to find the error or consult with your teaching assistant. When all results are correct, note them and log out of WebAssign. The InLab assignment must be completed by the end of the lab period. If additional time is required, please consult with your teaching assistant.

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Molecular Geometry QUIZ

25 questions

Introducing new   Paper mode

No student devices needed.   Know more

• 4. Multiple Choice Edit 1 minute 1 pt What is the geometric configuration of CO 2 ?  Bent  Trigonal planar Trigonal pyramidal Linear 
• 5. Multiple Choice Edit 45 seconds 1 pt What are all the bond angles in the linear arrangement as predicted by VSEPR theory?  90° 180° 120° 109.5°
• 6. Multiple Choice Edit 30 seconds 1 pt What is the name of pairs of electrons that do not participate in bonding?  outer pair unvalenced pair lone pair inner pair
• 10. Multiple Choice Edit 30 seconds 1 pt What is the measure of a tetrahedral bond angle? 90 Degrees 109.5 Degrees 120 Degrees 180 Degrees
• 11. Multiple Choice Edit 20 seconds 1 pt The bond angle for a trigonal planar molecule is  90 Degrees 109.5 Degrees 120 Degrees 180 Degrees
• 12. Multiple Choice Edit 30 seconds 1 pt How many unshared pairs of electrons will a bent molecule have?  1 2 3 4

What could this molecule be?

What could this be?

• 15. Multiple Choice Edit 1 minute 1 pt According to VSEPR, molecules adjust their shapes to keep which of the following as far away as possible? Pairs of valence electrons Inner shell electrons Mobile Electrons Electrons closest to the nucleus

Determine the molecular geometry of the given structure.

Trigonal Pyramidal

Trigonal Bipyramidal

Trigonal Planar

Tetrahedral

The geometry of a molecule with 3 bonded pairs of electrons and 0 lone pairs of electrons

The geometry of a molecule with 2 bonded pairs of electrons and 0 lone pairs of electrons

The geometry of a molecule with 4 bonded pairs of electrons and 0 lone pairs of electrons

Name the molecular shape of this molecule.

tetrahedral

trigonal bipyramidal

trigonal planar

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