In Recrystallization expirements why when using too much solvent does the crysta
ID: 857862 • Letter: I
Question
In Recrystallization expirements why when using too much solvent does the crystals not come out?
In Recrystallization when testing mulitple solvents for the best solvent to use.. Why when cooling the soltions after heating in water bath do crystals show up in more then one solvent? Shouldnt they only be appearing in the proper solvent?
I am just having a hard time visualizing whats happening in the beaker when the unknown solid dissolves (along with the impurities) into the solvent then the crystals form exluding the impurities... how do the impurities get left out wouldnt it just form the origional impure compund since all the molecules are floating dissolved in solvent? Or does the solvent bind to the impurities leaving only the pure compund to reassemble in a crystal lattice?
Sorry if these are stupid questions... just I am a visual person and am having a hard time understanding this...
Please help!
Explanation / Answer
In recrystallization process, solvent is choosen in such way solute and impurites are soluble in higher temperatures (not more than its boiling temperatures) and insoluble in lower temperature. Solubility is the miximum amount of solute soluble in given amount of solvent. For example solubility of solute A in water is 1 g per 100 mL at room temperature. So solute A crystals appear at less 100 mL water at less than room temperature. If we use too much solvent (more than 100 mL) at this conditions, the solute soluble in solvent and crystals disappers.
Therefore, When using too much solvent, the crystals not come out.
When testing multiple solvents for the best solvent:
The solvent in which solute is more soluble at hot condition and low soluble at cold codition is the best solvent. Thus, more crystals are appear in one solvent on cooling.
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