1. Why is the final product from the crystallization process isolated by vacuum

Question

1. Why is the final product from the crystallization process isolated by vacuum filtration and not by gravity filtration?
2. Imagine you failed to dry your purified benzoic acid sample completely. Tell how the error will affect your experimental results (yield, purity, or both) and explain why.
3. Explain, in your own words, why dissolving and then reforming crystals improves the purity of those crystals.
4. Explain why a solvent that can dissolve the solute, even when it is cold, is useless for recrystallizations.

Explanation / Answer

1) When we are using a vaccum, we are decrease the pressure from the lower side of the filter, keeping a big pressure difference which makes the solvent pass through the filter quickly, regardless of the amount of solution above the filter.This way we can minimize the residual amount of solvent in your solid product, but also avoid losses due to temperature increase like mentioned in the answer above.

2) when you failed to dry your purified benzoic acid sample completely.then the error in yield, and purity. mass of compound is more and yield goes on increases and you can get more percent yield and it also contain water making a less pure in nature.

3) The basic recrystallization plan is to dissolve an impure solid in a hot solvent, then cool the solution so that the desired molecules recrystallize while the impurities remain in solution. Subsequent filtration separates the solid crystal from the liquid solvent.temperature.so that the impurities are freed and purity of compound increases.

4) The basic recrystallization plan is to dissolve an impure solid in a hot solvent.if we use cold solvent the solute is not completely dissolved.

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