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October 21, 2009 | Chemistry -
Organic Chemistry I-Midterm Sample Exam Question
Lab instructors may use some of the following questions in their mid-term exam. When you study for the exam, please do not limit yourself to these questions and try to understand the experiments by reading the lab manual, your notebook and the power points posted on webct.
- Define melting point.
- What is the difference between melting point and melting point range?
- What is the difference between melting of a pure compound and melting of a mixture?
- What is eutectic temperature? Explain
- Explain the type of errors that can occur during melting point measurement.
- Do all organic compounds have melting point? Explain
- What is sublimation?
- What molecular forces are involved in an organic solid?
- In three sentences summarized what you learned in melting point experiment.
10. What type of error could happen during the melting point experiment?
11. Write down three safety rules.
12. Explain what is the difference between disposal of haloganted and non-halogenated organic solvents?
13. What is a halogenated solvent? Give an example.
14. In melting point experiment, what will happen if you pack the capillary tubes with large amount of solid?
15. What type of errors could occur during melting point measurement?
16. What is the difference between slow and rapid crystallization?
17. What will happen if you use too much solvent in recrystallization experiment?
18. Why you should determine the melting point of the crystals?
19. What is the purpose of the recrystallization, and how is done?
20. Name the recrystallization steps.
21. Why you should not wash the crystals with hot solvent?
22. What is the purpose of the washing the crystals with cold solvent?
23. What types of error could occur in recrystallization experiment?
24. What is the difference between the Buchner funnel and Hirsh funnel?
25. Define solvent, solute, and percent recovery.
26. Briefly explain how you would separate benzoinc acid from sand.
27. What is the purpose of distillation?
28. Summarized the distillation experiment in three sentences.
29. Explain effect of non-volatile impurity on vapor pressure of a volatile compound.
30. What is fractional distillation and were is used?
31. Sketch and completely label the apparatus required for a simple distillation.
32. Define the following terms: simple distillation, Raoult’s law, head temperature, ideal solution, pot temperature, Dalton’s law
33. Why should you never heat a closed system, and how does this rule apply to a distillation?
34. Explain the role of the stirbar that is normally added to a liquid that is to be heated to boiling.
35. In a miniscale distillation, the top of the mercury bulb of the thermometer placed at the head of a distillation apparatus should be adjacent to the exit opening to the condenser. Explain the effect on the observed temperature reading if the bulb is placed (a) below the opening to the condenser or (b) above the opening.
36. Distillation is frequently used to isolate the nonvolatile organic solute from a solution containing an organic solvent. Explain how this would be accomplished using a simple distillation.
37. Using Raoult’s and Dalton’s laws, explain why an aqueous NaCl solution will have a higher boiling point than pure water.
38. At 100 °C, the vapor pressures for water, methanol, and ethanol are 760, 2625, and 1694 torr, respectively. Which compound has the highest normal boiling point and which the lowest?
39. What is the formula and chemical structure of cyclohexane? Is this a halogenated solvent?
40. What is the difference in cis and trans isomers of an organic compound? Give an example.
41. What is the difference between single and double bond?
42. What are diastereomers?
43. What TLC stands for?
44. How does UV radiation effects carbon-carbon double bond?
45. What is an isomer?
46. What is the difference between cis and trans isomers of 1,2-dibenzoylethylene?
47. How Rf is calculated? Explain it.
48. What are stationary phase and mobile phase in TLC?
49. Why b-carotene and lycopene are soluble in organic solvent?
50. Why b-carotene and lycopene are both colorful.
51. What are the similarities and difference between TLC and column chromatography?
52. Is dichloromethane a halogenated solvent? How should it be disposed?
53. What is the purpose of magnesium sulfate in extraction of b-carotene and lycopene experiment?
54. Draw a column chromatography with sample and stationary phase (silica or alumina).
55. What is a mobile phase and stationary phase in column chromatography?
56. In extraction of b-carotene and lycopene experiment, what is the purpose of washing the food product with acetone?
57. In extraction of b-carotene and lycopene experiment, what is the purpose of dichloromethane?
58. Draw a vacuum filtration apparatus.
59. Draw a distillation apparatus.
60. What are three safety rules that you should follow in the lab?
61. Draw conjugated double bonds.
62. What is effect of double bond conjugation in interaction of organic compounds with electromagnetic radiation?