Term
| When do you use crystallization? |
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Definition
| When you want to purify componds which are sold at room teperatur. |
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Term
| What does the crystallization technique entail? |
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Definition
| Dissolvingthe material to be cystallized in a hot solvent and cooling the solution slowly. |
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Term
| Why do we heat then cool the solvent/compounds during crystallization? |
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Definition
| Because as you heat the mixture you dissolve the compound. Once its dissolved, cooling it takes advantage of the decreased solubility at lower temperatures and will separate from the solution during cooling (crystallize) |
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Term
| Explain the general procedure or crystallzation: |
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Definition
1) Dissolve solid in minimum amount of heated solent.
2) Hot filter solution to remove insoluble impurities
3) allow to cool and deposit crytals of the solid
4) Use vacuum filtration apparatus to separate supernatant solution and th crystals
5) rince crystals
6) allow crystals to dry to remove excess solvent. |
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Term
| Of a solute is very polar what kind of solvent will be required? |
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Definition
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Term
| "like dissolves like" refers to what? |
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Definition
| It refers to the fact that a polar solute will be dissolved by a polar solvent and tht a non-polar solute will be dissolved by a non-polar solvent. |
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Term
| What is hot filtration? when do you use it? |
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Definition
HF removes insoluble impurities when doing crystallization. Is a type of gravity filtration.
Large fluted filter paer/stemless funnel isemployed. Funnel and filter paper should be pre-heated. This avoids precipitation of the crystals. |
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Term
| What kind of flask do you use in crystallization |
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Definition
| Erlenmeyer flask - the narrow opening reduces the danger of contamination by dust |
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Term
| What type of funnel is used in the vaccuum filtration setup? |
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Definition
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Term
| What is the name of the compound that is crystallized in Part 1, Exp2? |
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Definition
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Term
| What is the impurity within the N-phenylacetamide compound in Exp2, part 1? |
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Definition
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Term
| What is the solvent used in part 1, exp 2 |
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Definition
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Term
| What are the two compounds added to the solution during crystallization in exp 2, part 1? |
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Definition
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Term
| When is distillation used? |
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Definition
| Technique for removing a solvent, purifying a liquid, or separating the components of a liquid mixture. |
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Term
| Explain the steps in distillation? |
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Definition
| A liquid is vaporized by boiling and then is condensed back into a liquid (the distillate). Components that boil at different temperatures are collected separately. |
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Term
| What is the normal boiling point. How do we correct for it? |
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Definition
Normal boiling point is measured at 760 Torr (1 atm).
The calculation is: ∆T=0.5℃ ∗(P_standard−P_observed)/(10 torr) and Normal b.p=Obs. B.P+ ∆T |
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Term
| What apparatus is used in determining melting point? |
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Definition
| The Gallenkamp Melting Point Apparatus. |
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Term
| How does the melting point indicate purity? |
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Definition
1) The purer the compound, the closer the top temperature of its melting point range to the literature value
2) The purer the compound, the narrower (sharper) the melting point range. |
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Term
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Definition
| It is defined as the separation of a mixture of two or more different compounds by distribution between two phases, one of which is stationary and one of which is moving. |
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Term
| What is column chromatography? What is it based on? |
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Definition
It is based on the difference between absorptivity of a compound onto the solid stationary phase and its solubility in the liquid mobile phase.
Ie if the substance has a high affinity for the stationary phase it will remain there (or near the top) and if it has a low affinity for the stationary phase / is soluble in liquid than will move through the column quickly. |
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Term
| What is silica gel a form of? |
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Definition
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Term
| Why is Silica Gel good for the stationary phase in chromatography? |
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Definition
| Because the silicon in silica gel terminates in a hydroxyl group...This forms a huge polymeric structure with a surface that comprises of many hydroxyl groups. This makes it a polar, stationary phase. |
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Term
| How do you calculate the Rf value ? |
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Definition
| Rf = distance traveled by substance/distance traveled by solvent front |
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Term
| What are the analgesic drugs used in Part D of experiment 3? |
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Definition
Acetylsalicylic Acid
Acetaminophen
Caffeine
Codeine |
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Term
| What are the types of plant pigments possible to be seen? |
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Definition
Green chlorins --> Chlorophyll A and B (B = more polar than A)
Yellow-Orange Carotenoids --> Two carotenes and three xanthophylls (Xanthophylls are more polar than carotenes) |
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Term
| What is the solvent used in Experiment #3, part A? separation of ink by column chromatography |
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Definition
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Term
| What is the solvent used in Experiment #3, part B? Separation of ink by TLC. |
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Definition
| 9:1 95% Ethanol: Acetic Acid |
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Term
| What type of beaker is used in Experiment 3, A-C, to create the development chambers? |
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Definition
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Term
| What is the solvent used in Experiment #3, Part C? (Separation of plant pigments) |
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Definition
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Term
| What is the solved used in Experiment #3, Part D? Analysis of Analgesics |
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Definition
| 25:1 Ethyl acetate: Acetic Acid |
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