If it were insoluble in hot temperatures the compound would not dissolve, where as it it was soluble in cold, crystallization would be a very unlikely process, To note, impurities should on the other hand be very soluble at room temperature and insoluble in hot eleven in order to be filtered out due to the fact they remain dissolved in the solvent where as the rest of the compound crystallizes when cooling.
2. How does rationalizations purify a solid? First a saturated solution is made(a compound containing impurities is dissolved in a hot solvent) -Secondly, the solution is cooled slowly(the slower, the bigger the eventual crystals), allowing solubility of compound to drop(not impurities solubility however), starting the crystallization process. (to note, to Start the crystallization of the compound a seed is often required which involves scratching he glassware until a nucleus Of glass provides a surface on Which crystals may begin to form) -Ideally by this step, solid equilibrium of impurities is not exceeded so crystals hue absolutely no impurities. In this case we could just filtrate discarding filtrate with all impurities) -However this is near impossible to achieve, impurities(however small an amount) make it into crystals. In this case we recitalist(heat and add water as solvent, cool, filtrate) again and again until pure. -Melting point helps indicate the amount of impurities in the crystals. (impurities lower expected melting point) 3. Briefly explain the significance of the melting-point results in regards to the purity of the crude and rationalized product.
The melting point for 100% pure acetaminophen should have been between 169-172 degrees Celsius.A melting point range of 151-154 was observed prior to rationalizations(signaling significant amounts of impurities), and a range of 161-165 after rationalizations(showing an improvement, and small purification leading to a decently pure product), 4, Suggest one chemical reason, specific to this experiment, why your percent recovery could be less than 100%. Initial rationalization of the saturated solution accounts for loss of product(a small percentage of the pure compound will not crystallize because it is not 100% insoluble at room temperature), also charcoal may absorb a small amount of product, though mostly absorbing impurities.In conclusion the more the compound is purified the less product is recovered. In this case the melting point and appearance points to quite a pure compound meaning to get to that desired state, much product would have been loosed in the process do to procedures.