Which of the following statements is correct about the reaction is given below?

4Fe(s)+3O2(g)2Fe2O3(g)

1. Total mass of iron and oxygen in reactants = total mass of iron and oxygen in product therefore it follows law of conservation of mass
2. Total mass of reactants = total mass of product, therefore, law of multiple proportions is followed
3. Amount of Fe2O3 can be increased by taking any one of the reactants (iron or oxygen) in excess.
4. Amount of Fe2O3 produced will decrease if the amount of any one of the reactants (iron or oxygen) is taken in excess.

1.  HINT: Limiting reagent concept
According to the law of conservation of mass,
Total mass of reactants = Total mass of products
Amount of Fe2O3 is decided by limiting reagent.