Answer: Nine moles of reactants form eight moles of product.
Step-by-step explanation:
According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.
As the subscripts in front of the chemical formulas represent the moles of the substances.Thus 8 moles of iron reacts with 1 mole of sulfur to give 8 moles of iron sulfide.