Sometimes, the melting point range of a sample does not correspond exactly to that recorded in the literature. Suggest four reasons why this might be the case.
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- If insoluble impurities, e.g., dust, tissue, filter paper, etc., were mixed with the sample, how would these affect the measured melting point?Briefly discuss how to identify the unknown compound by using mixed melting point method.estimate the composition of these initial samples of distillate using figure 1. Based on the results what conclusion can you draw regarding the relative efficiencies of the two separations?
- Based on the resulting chromatograms after visualization with iodine vapor, which between the solvent systems WHITE and MIX resulted in a more effective separation of the pigments of the indigo extract? Explain your answer in terms of the solvent that did not effectively separate the components of the root extract.Of Aspirin, ethanol, acetaminophen, ethyl acetate, hexane, and water which could go undetected during HPLC analysis, but could result in a lower than expected melting point, why are they not detected by HPLC analysis?What is the structure and IUPAC name of atrazine? The herbicide simazine is more polar than atrazine. In reverse phase chromatography of a solution containing a mixture of the two substances, which would elute first? Explain why this is in terms of partition. The instrument used in this practical exercise has a UV spectrophotometer as a detector. Give two other types of chromatographic detectors that might be used.
- The compounds biphenyl and naphthalene are presented in a mixture. Can hexane be used as a solvent to separate the compounds by column chromatography with silica gel as the stationary phase? Why or why not.What is the effect of weighing a recrystallized organic solid which is not completely dried to the percentage yield? Elaborate.A student recrystallized some impure benzoic acid and isolated it by filtration. He scraped the purified benzoic acid off the filter paper after it had dried and took the melting point as a test for purity. He was surprised that most of the white solid melted sharply between 121 and 122 0C but that a small amount remained unmelted even at temperatures above 200 0C. Explain this behavior.
- Compound A has a lower affinity for the stationary phase thancompound B and can dissolve well in the mobile phase. In theseparation of the mixture of A and B by column chromatography,which compound will be eluted first from the column? ExplainHow is "Characterization and spectroscopic techniques for analyzing" used in a melting point experiment?In addition to a low boiling point and immiscibility with water, why is density important to consider in the selection of an extraction solvent? Would an organic liquid with a density of 1.006 g/mL make a good extraction solvent? Explain.Write the chemical reaction that took place during this experiment.