Question

What possible reasons could be advanced that Jim recovered `82*g` of product that yielded `95*g`?

Answer 1

Clearly, Jim is a duffer in the lab.

Explanation:

In every chemical reaction ever performed, mass is conserved. If you start with `100*g` of reactants, at most you can get `100*g` of product. In practice you are not even going to get that. Reactions seldom proceed with `100%` yield, and even if they do, some losses are going to occur on handling, i.e. getting your product out of the reaction vessel, purifying it, getting it into a tared bottle; mass loss occurs down the line.

Here, Jim lost `(95-82)=13*g`. Jim was apparently a bit lax in scraping his product out of the reaction vessel; or maybe it didn't crystallize out of solution completely. If the product were pure, the loss may be acceptable.