[OhMyGawd]

Hello, I recently did a titration lab on Aspirin. Anyways, I calculated the solution would be titrated at 12mL. However, when I did the experiment I ended up with it being titrated at 12.1mL, I thought it was not a big deal since the 12.02mL is theoretical but my chem teacher had a fit and said it can't be over 12mL. So I added another drop and surely enough the solution went over-shot.

So is there a reason why my solution was titrated at 12.1mL? Also if it helps, the Aspirin is crushed and mixed with methanol and the base for the neutralization is Sodium Hydroxide. Can you also tell me any other errors why I got 12.1mL because I really can't think of any. I did hear however, that when a base reacts with air its molarity decreases - does this have anything to do with it?

[Borek]

Yes, NaOH can absorb atmospheric CO₂ and its molarity goes down, whether it influences titration results depends on the strength of the titrated acid.

However, aspirin titration can be a little bit difficult, as there is more than one reaction taking place. One is neutralization. Second is hydrolysis. Each have different stoichiometry. It is nothing unusual to use more NaOH than one expects.

[OhMyGawd]

Thanks for the response Borek! Also, would you only consider hydrolysis if water is used? Or does hydrolysis not take place if it is not water the reaction is being done with. Sorry I'm not that great at Chemistry .

[Borek]

Try to write reaction equation. it should explain a lot.