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Massachusetts Comprehensive Assessment System
2013, High School Chemistry
 Question 33: Open-Response |
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Reporting Category: Bonding and Reactions
Standard: 4.2 - Draw Lewis dot structures for simple molecules and ionic compounds.
Standard: 4.4 - Use valence-shell electron-pair repulsion theory (VSEPR) to predict the electron geometry (linear, trigonal planar, and tetrahedral) of simple molecules.
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Formaldehyde (CH2O) occurs in smoke from forest fires and in automobile exhaust.- Calculate the total number of valence electrons in one molecule of formaldehyde. Show your calculations.
Carbon is the central atom in a CH2O molecule.- Draw a Lewis dot structure for formaldehyde.
- Identify the shape of the formaldehyde molecule predicted by valence-shell electron-pair repulsion (VSEPR) theory. Explain your answer.
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Scoring Guide and Sample Student Work
Select a score point in the table below to view the sample student response.
| Score | Description |
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| 4 |
The response demonstrates a thorough understanding of how to use valence-shell electron-pair repulsion (VSEPR) theory to predict the molecular geometry of molecules. The response correctly calculates the total number of valence electrons in formaldehyde, draws a Lewis dot structure for formaldehyde, identifies the shape of the formaldehyde molecule, and clearly explains why formaldehyde has this shape. |
| 4 |
| 3 |
The response demonstrates a general understanding of how to use valence-shell electron-pair repulsion (VSEPR) theory to predict the molecular geometry of molecules. |
| 2 |
The response demonstrates a limited understanding of how to use valence-shell electron-pair repulsion (VSEPR) theory to predict the molecular geometry of molecules. |
| 1 |
The response demonstrates a minimal understanding of how to use valence-shell electron-pair repulsion (VSEPR) theory to predict the molecular geometry of molecules. |
| 0 |
Response is incorrect or contains some correct work that is irrelevant to the skill or concept being measured. |
Note: There are 2 sample student responses for Score Point 4.
High School Chemistry
- Question 11: Bonding and Reactions
- Question 23: Properties of Matter and Thermochemistry
- Question 33: Bonding and Reactions
- Question 44: Atomic Structure and Periodicity
- Question 45: Solutions, Equilibrium, and Acid-Base Theory
Return to the MCAS 2013 Student Work Directory
Last Updated: August 6, 2012
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