Midterm_1_W11_Key

Midterm_1_W11_Key - Chem 6AL W11 Russak 24 January...

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Unformatted text preview: Chem 6AL W11 Russak 24 January 2011 Midterm 1 KEY  ­The following questions are all multiple choice.  ­Write and bubble in your perm #, write your name  ­You may only have a pen/pencil and a simple calculator, nothing else.  ­No phones or iPods  ­No hats/hoods 1. Which is not required of a student in the lab environment here at UCSB a. Shoes b. Goggles c. Lab Notebook d. Lab Coat e. All of the above are requirements 2. Which of the following would be acceptable to put down the sink drain in the lab? a. Acetone b. Cinnamic acid c. Urea d. Ethanol e. None of the above can be put down the drain 3. A pure gold crown is tested to determine its density. It is found to displace 10.7 mL of water and has a mass of 206 g. What is the density of gold? a. 19.25 g/mL b. 5.19 x 10 ­2 g/mL c. 5.2 x 10 ­2 g/mL d. 19.3 g/mL e. None of the above 4. A student performing the melting point of a sample of pure benzoic acid (literature MP = 122 ­123 °C) achieved a range of 110 ­112 °C. What was the most likely cause of the error? a. The sample most likely contained impurities caused by contamination from another student b. The melting point apparatus was increasing too rapidly in temperature c. The sample reflects benzoic acid at its eutectic point with another material d. Both a and c e. None of the above 5. A soon to be bride takes her ring to the jeweler because she suspects her fiancé of cheeping out. The jeweler finds that the refractive index is 2.20. If the speed of light that travels through diamond is 1.24 x 108 m/s, is this a fraud? a. No, she can go ahead and get married b. No, because diamond would have a lower refractive index c. No, because a refractive index of lower that 1 is impossible d. Yes, because a refractive index of greater than 1 is impossible e. Yes, because diamond would have a higher refractive index 6. The refractive index of Cyclohexane is 1.287 and the refractive index of toluene is 1.497. Based on this, which compound does light move the slowest through? a. Toluene b. Cyclohexane c. Light always travels at the same speed. 7. What is always true about the range of a melting point? a. A broad range is indicative of a pure compound b. The range is not an indicator of purity c. A sharp range is always indicative of a pure compound d. The broader the range, the more impure the compound e. None of the above 8. Suppose you mix 5.00 g of benzoic acid (122.12 g/mol) with 4.00 g mandelic acid (152.15 g/mol). What is the wt % of mandelic acid in benzoic acid? a. 55.55 wt % b. 55.6 wt % c. 44.44 wt % d. 44.4 wt % e. None of the above 9. What is the mol percentage of benzoic acid in mandelic acid? a. 60.89 mol % b. 60.9 mol % c. 64.22 mol % d. 64.2 mol % e. None of the above 10. Benzoic acid has a melting point of 122 ­123 °C and mandelic acid has a melting point of 120 ­122 °C. Ignoring any eutectic phenomena, what will happen to the melting point if the two compounds are mixed? a. The melting point of the mixture will be higher than that of the literature values b. The melting point of the mixture will be lower than that of the literature values c. The melting point will be the same because both compounds have about the same melting point d. The melting point will be higher and broader because impurities cause broadness in the range. e. None of the above are acceptable answers 11. Which of the following is not a colligative property a. Boiling point elevation b. Melting point depression c. Boiling point depression d. Freezing point depression e. All of the above are colligative properties 12. What is the mathematical definition of percent error? a. (experimental/literature) x 100 b. [(|literature ­experimental|)/experimental] x 100 c. [(|experimental ­literature|)/experimental] x 100 d. [(|literature ­experimental|)/literature] x 100 e. None of the above are the proper mathematical definition of percent error 13. When preparing a sample for a melting point, how high should the solid fill in the capillary tube? a. 1 ­2 mm b. 1 ­2 cm c. At least 5 mm d. At least 5 cm e. None of the above are correct answers 14. Identify the proper way to report a melting point by specifying the starting and ending point that should be recorded. A a. b. c. d. e. B C D E A and E B and D B and E C and E D and E 15. Identify the following functional group a. b. c. d. e. Aldehyde Ketone Ester Ether None of the above O O 16. Identify the following functional group a. Amide b. Amine c. Ketamine d. Ketone e. None of the above 17. Identify the following functional group a. b. c. d. e. Amide Anhydride Carbonic acid Diacetic acid None of the above O O N H O O Infrared Spectroscopy 18. Which of the following functional groups has the highest bond order? a. Acid chloride b. Aldehyde c. Amide d. Ketone e. Ester 19. Which would have the lowest ring strain? a. Cyclopropanone b. Cyclohexanone c. Cyclobutanone d. Cyclopentanone e. All have equal ring strain 20. Conjugation will have what effect on a carbonyl stretch? a. It will increase the energy b. It will increase the wavenumber c. It will lower the wavenumber d. It will lower the energy e. C and D are both correct answers 21. What law explains the principle of Infrared Spectroscopy and the “stretch” infrared light imposes on a bond? a. The photoelectric effect b. Hooke’s Law c. Boyle’s Law d. Charles’ Law e. None of the following laws correlate with Infrared Spectroscopy Match the following structures to their respective spectra. Answers in order = CDBAE OH OH A B C D E 22. 23. OH OH A B C D E 24. 25. OH OH A B C D E 26. Equations: N=c/ʋ Vibration Alkanes CȺH stretch CȺH bend Alkenes C=CȺH stretch C=C stretch C=CȺH bend Alkynes C≡CȺH stretch C≡C stretch Aromatic Compounds CȺH stretch C=C stretch CȺH bend Alcohols OȺH stretch CȺO stretch E=hc/λ h=6.626 E ­34 J.s c = 3.00 E8 m/s d=m/V  ­1 Position (cm ) 2990 ­2850 1480 ­1430 and 1395 ­1340 3100 ­3000 1680 ­1620 sat, 1650 ­1600 conj 995 ­685 3310 ­3200 2250 ­2100 3100 ­3000 1620 ­1440 900 ­680 3650 ­3550 non ­hydrogen bonded 3550 ­3200 hydrogen bonded 1300 ­1000 Amines 3550 ­3250 NȺH stretch Nitriles 2280 ­2200 C≡N stretch Aldehydes 2900 ­2800 and 2800 ­2700 CȺH stretch 1740 ­1720 sat, 1715 ­1680 conj C=O stretch Ketones C=O stretch 1750 ­1705 sat, 1715 ­1650 conj Esters C=O stretch 1765 ­1735 sat, 1730 ­1715 conj 1300 ­1000 CȺO stretch Carboxylic Acids 3200 ­2500 OȺH stretch 1725 ­1700 sat, 1715 ­1680 conj C=O stretch 1300 ­1000 CȺO stretch Amides 3500 ­3150 NȺH stretch 1700 ­1630 C=O stretch Anhydrides C=O stretch 1850 ­1800 and 1790 ­1740 1300 ­1000 CȺO stretch Acid Chlorides C=O stretch 1815 ­1770 Nitro Compounds NO2 stretch 1570 ­1490 and 1390 ­1300 s = strong, m = medium, w = weak, br = broad, sat = saturated, conj = conjugated Intensity m to s m to w m w to m s s m to w m to w m to w s m br, s s br, m s w, Fermi Doublet s s s br, m to w s s m s s s s s ...
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This note was uploaded on 04/09/2011 for the course CHEM 6a taught by Professor Pettus during the Winter '07 term at UCSB.

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