Question

A 0.5000g sample of FeO is ignited to Fe2O3; what is the percentage gain in weight?

Answer 1

Assuming no losses, the sample of Fe2O3 will have a mass of
0.5000 x (molar mass Fe2O3/2*molar mass FeO) = ?
Weight gain is the difference between ? and 0.5000 = let's say y.
Then % gain = 100y/0.5000 = ?

Answer 2

You must be a fairly good typist; you typed four (4) questions in less than a minute. Also I note you didn't send a lot of time telling how you thought the problems might be solved.