A 6.25 g sample of magnetite (Fe3O4) contains 4.52 g of Fe. What is the mass percent of iron in magnetite?

When balancing a chemical equation:

Which material burns faster? metal aluminum

What would be the original temperature of a gas that has a volume of 2.0 l and a pressure of 2.0 atm and an unknown temperature that the volume increased to 3.5 l in its pressure decreased to 1.0 atm if the final temperature is measured to be 11°c