Question

A student is doing part B of the procedure and decides to skip the step that asks him to check for completion because they don't understand it. Later in part C they find that the precipitate formed does not act entirely like the FeS that he was expecting to get and his results were kind of vague. What is the most logical explaining for their results?

Answer 1

First to all I need you to put the whole procedure or experiment to understand it better. But the most logical thing that it happens here, is that he didn't check that the reaction goes in completion. A reaction that is complete generates the final product with no reactants remaining. So, when a reaction is not complete, it means that the reaction is in equilbrium with it's products and reactants. And probably that's what happens here.

The reaction didn't complete, and when he goes to part C, the product obtained was one product of the equilibrium reaction of part B. Maybe one reactant of that reaction, was the one to react in part C and therefore, the product formed was different than FeS. maybe it's a derivate of that product.

Hope this helps