Organic Chem Lab - Quiz Questions and Answers found online

Organic Chem Lab - Quiz Questions and Answers found online...

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Representative Questions for Quiz 1 Why should you not use a solvent (other than water) to remove chemicals from your skin? - This will hasten absorption of chemical through the skin Why is it important to prevent a person with burning clothing from running? - The greatest harm comes from breathing the hot vapors that rise past the mouth How should a fire extinguisher be directed when trying to put out a fire? - Aim it at the base of the fire & squeeze the handle and don t hold on to the horn b/c it will become cold A very small fire in a beaker or a flask could possibly be put out by simply covering the vessel with a flat object. Why is this possible? - A wire gauze or watch glass could put out a small fire b/c it will prevent oxygen from fueling the fire Why is it dangerous to wear contact lenses in an organic chemistry laboratory? (Be specific) - The lenses could be fused to one s eyes Why would placement of too much sample into a melting point capillary tube cause an inaccurate melting point to be observed? - Too much will cause differential in temperature throughout the sample Why would coarse particles in a melting point sample cause an inaccurate melting point to be observed? - Coarse particles will cause air pockets which will cause an inaccurate temperature Define eutectic point in terms of the two components of a mixture and their liquid solutions. - The pt. at which x & y & their liquid solutions are in equilibrium You have carried out an experiment that has produced a new unknown compound Y. Which of the 3 reasons for a melting point determination would best describe why you would take the melting point of compound Y? - 1) characterize a known compound 2) record a physical characteristic for a new compound 3) establish the purity of a compound (impure one will have lower and wider range of temp.) Define eutectic point with respect to melting point composition diagram. - lowest pt. on graph in which the mixture a narrow point List two effects of the recrystallization process on the melting point (range) of a solid. - 1) cause a narrower mp range 2) purify it 3) mp range will be displaced upward Anthracene (look up structure) has a much higher melting point than naphthalene (look up structure). What reason would be the main reason for the higher melting point? - Anthracene has more conjugated double bonds In the "Hints for preparation", you were instructed to make sure that the temperature of the Mel-Temp apparatus was 80°C or lower before inserting a sample of pure urea (mp. 132.5°-133°C) into the slot in the Mel-Temp. Why was it important that the Mel-Temp temperature be so much lower than the sample's
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melting point to get an accurate melting point? (Be specific) (NOTE: “Because the sample will melt immediately if the Mel - Temp is too hot” is not the answer) - the tube had to be heated slowly and gradually for an accurate measurement of mp What condition does a solid impurity have to satisfy in order to depress a compound's melting point?
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