ATAR Notes: Forum

VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: Christiano on June 21, 2011, 08:46:22 pm

Title: Aspirin SAC (yes, it's late)
Post by: Christiano on June 21, 2011, 08:46:22 pm

Alright so we're doing the aspirin write up tomorrow, and I'm not sure about this question:

Instead of using the solvent we used in the prac, pretend your using solvent X. Salyclic is less soluble in this solvent than aspirin. Can this be solvent be used to purify by “recrystallization”. Explain.

It's 2 marks and I believe you can go either way. The original solvent was an ethanol/water mixture.

Title: Re: Aspirin SAC (yes, it's late)
Post by: Mao on June 21, 2011, 10:33:43 pm

No. Recrystallization relies on dissolving the impure crystal, then forming a new pure crystal. If salicylic acid is less soluble than aspirin, then it will crystallize first (roughly speaking). Any subsequent crystallization of aspirin would mean there are salicylic acid impurities in there, which defeats the purpose of a recryst.