What is likely to have occurred if a calculated percent yield is larger than 100%?

Question

Limiting Reactant Questions

Answer 1

Other than an obvious math error, there can be an experimental error, where the mass of the product is over estimated.  This can occur, for example, if the product has impurities in it, such as water.  If the product isn't dried to constant weight, then some of the water associated with it is weighed as "product", and this will lead to an overestimate of the mass of the product and and overestimate of the % yield.