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O Chem
First Midterm for Organic Chemistry Unit 1
| Question | Answer |
|---|---|
| What types of organic reactions require heating? | Those that are very slow at room temperature, (Endothermic) |
| What types of organic reactions require cooling? | Those that are exothermic at room temperature |
| In what manner do liquids boil when heated in laboratory glassware? | They tend to bump |
| Why is the addition of boiling stone to a hot liquid ill-advised? | The hot liquid may suddenly boil, likely erupting from the flask |
| What manner of stirring makes the use of boiling stones unnecessary | Magnetic stirring |
| Why should one pour a flammable liquid only after all hot heating devices have been removed from the work area? | The contact with a hot heating device and liquid at it's flash point exceeded the liquid could ignite |
| Why is is unwise to heat a flammable liquid in an open container on a hot plate. | The hot plate's thermostat may provide an ignition source resulting in a fire |
| What are the features of a typical aluminum heating block? | Openings to accommodate: 1.Reaction tubes 2.Reaction vials 3.Round-bottomed flasks 4.a thermometer |
| Under what circumstances are cooling baths used? | When it is desirable to: 1.regulate an exothermic reaction 2.cool a reaction mixture prior to a subsequent part of the procedure 3.promote complete crystallization |
| What are common cooling systems? | 1. cold tap water 2. an ice-water mixture |
| Does the use of crushed ice alone provide efficient cooling? | No, since air pockets do not conduct heat very well. |
| Why do most organic reactions require a period of heating? | They are too slow at room temperature |
| What is meant by the term 'refluxing' | This term refers to the process of boiling a sol'n in such a way that the volatile components are condensed thereby allowing them to return to the reaction flask |
| what types of condensers are commonly used as part of a reflux apparatus | 1. water jacketed condensers( used when boiling at <150 degrees c) 2. air jacketed condensers( used when boiling at <100 degrees c) |
| What is a likely consequence of refluxing too vigorously? | The capacity of the condenser will be exceeded resulting in the loss of volatile reagents and/or products |
| How are liquids added to the flask of the reflux apparatus? How are solids added to the flask? | Conical funnels are used to add liquids; powder funnels are used to add solids. |
| What steps constitute a typical solid-liquid extraction? | 1.add solid mixture to a suitable flask 2.add extraction solvent 3.outfitting the flask for heating under reflux 4.reflux the suspension 5.cool the suspension 6.isolate filtrate by gravity filtration 7.remove solvent by evaporation |
| What characterizes an effective solid-liquid extraction solvent? | 1. desired component is highly soluble in the solvent while other components are not. 2.solvent should be chemically inert 3.After extraction, solvent should be readily separable from the solute. |
| What are the four principles of weak intermolecular interactions? What are their relative strengths? | 1.hydrogen bonding(strongest) 2.dipole-dipole interactions 3.dipole-induced dipole interactions 4.induced dipole-induced dipole interactions(Weakest) |
| What characterizes the reorganization of molecules as a crystalline sample melts? | The molecules reorganize from fixed, orderly arrays in solids to random motion in liquids |
| What aspects about a compound can be established from its melting point? | 1.identity 2.purity |
Created by:
jackscam
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