McMinn

Study Guide -- Lab 3

After reading pages 601-618,620-629, 754-769, and Part B of Handout 1, you should be able to do the following:
1. Describe how a crystallization can be used to purify an organic compound from soluble and insoluble impurities.

2. Describe the ideal solubility behavior of desired substance and impurities for a crystallization 3. Define solute and mother liquor. 4. Use the theory of crystallization to calculate the composition of the mother liquor and the solid obtained after successive crystallizations. 5. Identify which mixtures can be successfully separated via a crystallization and which can not. 6. List the four main steps in a microscale crystallization using a Craig tube (Figure 5.5).

a. Explain why the hot solvent should be added dropwise to the solute. b. Describe two methods to remove insoluble impurities. Explain how to prepare and use a filtering pipet (pages 591-592).

c. Explain how to isolate crystals from a Craig tube using centrifugation (pages 598-600). Note we will not use a Hirsh funnel as suggested in the handout. 7. Identify situations that require a decolorization step. 8. List several techniques to induce crystallization. 9. List two ways the melting point of a compound isused by the organic chemist. 10. List two ways the melting point indicates the purity of a sample. 11. Recognize that melting points are usually given as a range of temperatures. 12. Explain how to pack a melting point tube. 13. State what the acronym TLC stands for. 14. Outline the principles of TLC. 15. Describe how to prepare a micropipet (Fig. 14.3).16. Describe how to spot a TLC plate (Fig.14.4) 17. Describe how to use a development chamber for TLC. 18. Describe two common visualization methods for TLC. 19. Explain how to calculate the Rf value and how the Rf value is used. 20. List six applications of TLC in organic chemistry.