Midterm_1_M11_Key - Chem 6AL M11 Russak 18 July 2011...

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Unformatted text preview: Chem 6AL M11 Russak 18 July 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. In the laboratory, what is the proper disposal method for organic waste a. It’s organic, so it can go down the sink b. The trash bin c. Incineration in the hood d. In a properly labeled bottle in the hood e. None of the above 2. Why is it better to wear a cotton lab coat as opposed to a synthetic one? a. Each material is perfectly fine for a lab coat b. Cotton is less susceptible to fire/heat than synthetic material c. Cotton will melt instead of catch on fire d. Cotton lab coats are much less expensive e. None of the above 3. A fellow student is using an open flame in lab and their sweater catches on fire. Which is the best safety feature to use in the lab for this scenario? a. Fire blanket b. Fire extinguisher c. Safety shower d. First aid kit e. None of the above 4. Which of the following properties is not considered a colligative property? a. Melting Point b. Osmotic Pressure c. Freezing Point d. Refractive Index e. None of the above are considered colligative properties 5. According to the laws of colligative properties, adding NaCl to water would a. Increase the boiling point of the solution b. Decrease the boiling point of the solution c. Increase the melting point of the solution d. Both B and C e. None of the above 6. Which separation technique is most applicable to hydrocarbons such as those in crude oil? a. Extraction b. Distillation c. Recrystallization d. Filtration e. All of the above 7. 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. 8. In experiment 1, a melting point was taken of a 12.0 mol % sample of cinnamic acid (148.16 g/mol) in urea (60.06 g/mol). What is this mixture in wt %? a. 5.2 wt % b. 25.1 wt % c. 25.2 wt % d. 52.4 wt % e. None of the above 9. A solution of 2.00 grams of ethanol (46.00 g/mol) and 3.00 grams of methanol (32.04 g/mol) was prepared. Assuming the pure vapor pressure of methanol is 81 kPa and the total vapor pressure for the system is 69.5 kPa, what is the pure vapor pressure of ethanol? a. 11.5 kPa b. 22.1 kPa c. 35.7 kPa d. 44.7 kPa e. None of the above 10. Consider a 48.3 wt % mixture of hexane (86.0 g/mol, P°=72.0 kPa) in toluene (92.0 g/mol P°=35.0 kPa). What is the combined vapor pressure? a. 52.9 kPa b. 53.5 kPa c. 54.1 kPa d. 55.6 kPa e. None of the above 11. 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 12. 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 13. 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 14. Ethanol, when distilled from water, is only able to reach roughly 96% purity. What phenomenon is responsible for this? a. Freezing point depression b. Azeotrope c. Eutectic point d. Rault’s Law e. All of the above 15. A student prepared a melting point sample by placing ~5mm of sample in the capillary tube. Upon observation of the melting point, a range of 124 ­137 °C was measured. Based on this information, there is no way to tell if the compound is pure or impure. a. True b. False 16. 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 17. Identify the following functional group a. b. c. d. e. Amide Amine Ester Ketone None of the above O R NH2 18. Identify the following functional group a. b. c. d. e. Amide chloride Anhydride Carbonic acid Diacetic acid None of the above O R Cl 19. When sodium hydroxide is added to acetic acid (pKa = 5), there are how many molecules of sodium acetate per molecule of acetic acid? a. 1 b. 1010 c. 1021 d. 10 ­10 e. None of the above 20. Which organic solvent would constitute the bottom layer when performing an extraction with water? a. Ethyl Acetate b. Hexanes c. Chloroform d. Toluene e. None of the above 21. The reason recrystallization works to purify a compound is because a. Impurities are highly concentrated in the solvent b. The solute is lowly concentrated in the solvent c. Impurities are lowly concentrated in the solvent d. The concentration has no effect on the ability to crystallize the compound e. None of the above Infrared Spectroscopy 22. Which of the following functional groups has the lowest bond order? a. Acid chloride b. Aldehyde Fermi Resonance c. Amide NH stretch d. Ketone carbonyl e. Ester C ­O stretch 23. Which would have the lowest amount of ring strain? a. Cyclopropanone b. Cyclohexanone c. Cyclobutanone d. Cyclopentanone e. All have equal ring strain 24. A stretch in the infrared shows a stretch at 6.063 x 10 ­20 Joules. This corresponds to the stretch of what functional group? a. Sp hybridized C ­H stretch b. Sp2 hybridized C ­H stretch c. Sp3 hybridized C ­H stretch d. C ­O stretch of an ether e. C=O stretch of a ketone 25. 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 Match the following structures to their Infrared Spectra: ANSWERS: 26C, 27E, 28B, 29A, 30D O2N NO 2 O NO2 A 26. B C D E O2N NO 2 O NO2 A B C 27. D E 28. O2N NO 2 O NO2 A 29. 30. B C D E Equations: N=c/ʋ E=hc/λ h=6.626 E ­34 J.s c = 3.00 E8 m/s d=m/V P=P°X P=PA+PB Υ=P/Ptotal K = [A]org / [A]aq [A]aq final / [A]aq initial = [(V2/(V2+V1K)]n 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  ­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 NȺH stretch 3550 ­3250 Nitriles C≡N stretch 2280 ­2200 Aldehydes CȺH stretch 2900 ­2800 and 2800 ­2700 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 CȺO stretch 1300 ­1000 Carboxylic Acids OȺH stretch 3200 ­2500 1725 ­1700 sat, 1715 ­1680 conj C=O stretch 1300 ­1000 CȺO stretch Amides NȺH stretch 3500 ­3150 1700 ­1630 C=O stretch Anhydrides C=O stretch 1850 ­1800 and 1790 ­1740 CȺO stretch 1300 ­1000 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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