[ALMOS7]

So in my lab we were synthesizing ASA (aspirin). I started with 2.22g of salicylic acid (Molar mass 136g/mol) and I ended up with 3.538g/mol of ASA (molar mass 180g/mol). This means that my actual yield is over 120%, which is peculiar.

I lost some of the ASA product here and there, and so I assumed I would get less than a perfect yield. I spent 10 mins drying the product in a buchner funnel filtration setup (some even fell through the filter paper), and then put the ASA onto a clear watch glass and dabbed it really hard with filter paper multiple times to get the moisture out.

After all of the effort, is it possible that there was still a lot of moisture in the final product? What other kind of impurities could be in my yield, adding to the weight? I added 5.00ml of acetic anhydride and about 5 drops of phosphoric acid and a lot of water during the experiment, just like the instructions told me to.

[Arkcon]

I think you've guessed it correctly, you very likely have more moisture in your product than you expected.  If we're going to analyze a sample of acetylsalicylic acid according to USP (US Pharmacopeia, that means to test a sample for use as a medicine in the US) we would store it in a desiccator over silica gel for 5 hours, even if we just too purified material from a bottle, never mind recently synthesized.  Sadly, this compound isn't really very stable.  I wouldn't be allowed to use it after a day, but maybe, if you kept your product open overnight, you'll find that its lost its volatile impurities, and you'll get a better result.