0Hat the accepted melting point should be, how can you tull, Iróm your mp data,
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0Hat the accepted melting point should be, how can you tull, Iróm your mp data, whether the final sample is pure Post-Lab Questions: Explain the purpose of each of the following: a) 1. One step of the recrystallization involves hot, gravity filtration. Explain why the filtration must be done while the solvent is hot b) Explain why gravity filtration rather than suction filtration is used. c) Explain why the crystals in the final step must be washed with cold solvent. 2. If a little activated charcoal does a good job removing impurities in a re- crystallization, why not use a lot? Explain your answer. Even if your technique were excellent why should you not expect 100% recovery? Be specific. 3. (post-lab questions continued next page)Explanation / Answer
Activated charcoal also known as activated carbon is a specially prepared form of Carbon designed to have numerous small pores all over its surface. The pores bascially serve the function of increasing the surface area of the Activated Carbon.
The mechanism through which the Activated Carbon removes the impurities present in the solution is through surface adsorption. (i.e Activated Carbon holds the impurity molecules in a form of a thin film over its surface. Greater the surface area, more is the holding capacity.)
Now if too much Activated Carbon is used, what essentially happens is the impurities are completely removed from the solution, but there still is a lot of space (surface area) that is unfilled. Activated Charcoal will then adsorb molecules that we are interested in and thus will reduce the product yield.
That is why it is prudent to not overuse Activated Carbon during Recrystallization.
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