Question

What effect would over titrating have on the calculated moles on NaOH

Answer 1

Can you elaborate on the experiment please?

Answer 2

Excess amount of OH\(^-\) ions present in the solution. Generally in a titration curve, you have a sinusoidal type behavior. But, again, this depends on the type of titration you're doing, and you would need to elaborate more. There are more than one type of titration methods used in chemical analysis.