Midterm 1_KEY_F08

Midterm 1_KEY_F08 - Name_GSI_ KEY Chemistry 1A, Fall 2008...

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Name_____________________GSI__________ Page 1 of 7 KEY Chemistry 1A, Fall 2008 Midterm Exam #1 September 16, 2008 (90 min, closed book) Name:__________________________________ SID:___________________________________ GSI Name:________________ The test consists of 4 short answer questions and 15 multiple choice questions. Put your written answers in the boxes provided. Answers outside the boxes may not be considered in grading. Write your name on every page of the exam. Question Page Points Score Question A 2 12 Question B 3 10 Question C 4 12 Question D 5 6 Multiple Choice 6 30 Total 70 Useful Equations and Constants: PV = nRT () nRT nb V V n a P = + 2 2 2 2 1 mv KE = P total = P A + P B = X A P A ° + X B P B ° N 0 = 6.02214 x 10 23 mol -1 T (K) = T (°C) + 273.15 R = 0.0821 L atm K -1 mol -1 1 atm = 760 mm Hg = 760 torr 1 bar
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Name_____________________GSI__________ Page 2 of 7 A) Isomers There are three containers in the lab that are all labeled “contains pure C 3 H 4 ”. Using your new found knowledge of structures you determine that the containers could contain these three molecules: methylacetylene, 1,2-propadiene, and cyclopropene. Based on the structures below and the data presented, you can determine which substance is in each container. methylacetylene 1,2-propadiene cyclopropene CCC H H H H H H H H C C C H H H H The substances in Containers 1 and 3 are soluble in water but the substance in Container 2 is not. What is the material in Container 2? (circle one) methylacetylene 1,2-propadiene cyclopropene Explain your choice in terms of molecular structure and macroscopic properties. Solubility increases with the strength of intermolecular forces. In general, “like will dissolve like.” 1,2-propadiene is non polar so would not dissolve in water because water is polar. Methylacetylene and cyclopropene are slightly polar due to their geometry, so they dissolve in water. To determine the relative boiling points of the substances, you gently heat the substance in Container 1. Instead of turning into vapor it reacts to form a stringy mess. Which substance would you think would be the most unstable? (circle one) methylacetylene
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Midterm 1_KEY_F08 - Name_GSI_ KEY Chemistry 1A, Fall 2008...

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