Are you talking about the salicylic acid lab? If so, in the next lab (where you synthesize asprin), when I was in CHEM 281, we were provided with salicylic acid if we didn't have enough. Also, the percent yield is part of the marking scheme in the lab reports, but its not everything. If you have the rest of the lab correct, I wouldn't worry about it. As for repeating labs, I'm sure you can, if there are still labs going on that week (I did it in the Fall, where there were multiple labs going on throughout the week). If not, I don't really know, but theres no harm in asking.
I suggest you email Dr. Merbouh and explain what happend.
I'm not sure which experiments they did this for anymore since it was a while back, but I know they gave people more of a compound if they didn't have enough to continue on. But the lab portion of the course is only 25% total anyways - I doubt 2 poor yields would kill that.
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I suggest you email Dr. Merbouh and explain what happend.