# How many?

Chemistry Level pending

Heated $$m$$ (g) $$\ce{Fe}$$ in the oxygen we received $$3\text{ g}$$ mixed of $$X$$ included $$\ce{Fe_{3}O_{4}}; \ce{FeO}$$ and $$\ce{Fe}$$ still remain. Dissolved $$X$$ in hot concentrated of $$\ce{H_{2}SO_{4}}$$ we received 0,84 liters of $$\ce{SO_{2}}$$ in standard conditions. Find $$m$$.

×