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In a recrystallization from ethanol, acetyl salicylic acid (pure mp 137- 138 degree C) was melted on a melting point machine immediately after vacuum filtration, and found to have a melting point of 120-127 degree C. Why is the melting point not 137-138 degree C? Assume that there are no solid compounds present other than acetyl salicylic acid, and explain in terms of what affects melting points, and how. Why should the funnel be stemless when performing a hot gravity filtration? Construct a flow chart showing the purification of aspirin. Begin with aspirin, soluble impurities, and insoluble impurities. What is the purpose of evaporating some of the solvent before cooling to get crystals? Drawing air through the crystals aids in drying them. How do we accomplish this? It is important when a vacuum filtration is finished to disconnect the vacuum hose before shutting off the water. What will happen if you neglect to do this? Would ammonium carbonate (smelling salts) dissolve better in water, or in ethanol? Why?
In a recrystallization from ethanol, acetyl salicylic acid (pure mp 137- 138 degree C) was melted on a melting point machine immediately after vacuum filtration, and found to have a melting point of 120-127 degree C. Why is the melting point not 137-138 degree C? Assume that there are no solid compounds present other than acetyl salicylic acid, and explain in terms of what affects melting points, and how. Why should the funnel be stemless when performing a hot gravity filtration? Construct a flow chart showing the purification of aspirin. Begin with aspirin, soluble impurities, and insoluble impurities. What is the purpose of evaporating some of the solvent before cooling to get crystals? Drawing air through the crystals aids in drying them. How do we accomplish this? It is important when a vacuum filtration is finished to disconnect the vacuum hose before shutting off the water. What will happen if you neglect to do this? Would ammonium carbonate (smelling salts) dissolve better in water, or in ethanol? Why?
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