In this experiment, you will examine crystallization and recrystallization as a purification technique. ÆCrystallization and recrystallization are used extensively for the isolation and purification of organic and inorganic compounds. ÆThe technique exploits the differences in solubility of the components in a mixture. The desired compound is crystallized while impurities remain in solution.Note:Time management will be critical with this lab, so be sure to follow the lab manual and your TA’s instructions regarding multi-tasking so that you can finish the experiment.
Fig 17.5, pg 838 in ZumdahlFe(NH4)2(SO4)2.6H2Owill have a similar trend to the KCl line shown here.
has intentionally blurred sections.
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ProblemConsider the problem of separating a mixture consisting of 200 grams of KNO3(target compound) and 10 grams of (NH4)2Fe(SO4)2.6H2O (impurity). ApproachCooling from 95ºC to 0ºC…Æ10 g KNO3(aq) remain in solution at 0ºC because of the solubility of KNO3(see Fig 17.5 on the previous slide or Figure 1 on pg 46 of the lab manual)Æ190 g KNO3(s) crystallizeÆ10 g of (NH4)2Fe(SO4)2· 6H2O (aq) remain in solutionÆFilter and dry the nearlypure KNO3•a small amount of (NH4)2Fe(SO4)2.6H2O (aq) may get trapped in the KNO3crystals, but only a small amount considerably less than the 10 g original amount