Question

Calculate The scientist repeats the experiment, burning a new sample of steel wool until it is entirely converted into iron oxide. The iron oxide produced has a mass of 715 g. What was the mass of the sample before burning?

Answer 1

Which iron oxide; i.e., is that FeO or Fe2O3? I assume that's Fe2O3 so

4Fe + 3O2 --> 2Fe2O3
Convert 715 g Fe2O3 to Fe this way:
715 g Fe2O3 x (4* atomic mass Fe/2*molar mass Fe2O3) = 715 x 2 = ? grams Fe.