Final answer:
The amount of product formed in a reaction is determined by the limiting reactant.
Step-by-step explanation:
The amount of product formed in a reaction is determined by the limiting reactant. The limiting reactant is the reactant that is completely consumed in a reaction, thus limiting the amount of product that can be formed. Let's say we have a reaction between hydrogen gas and oxygen gas to form water. If we have 4 moles of hydrogen and 2 moles of oxygen, the balanced chemical equation tells us that we need 2 moles of hydrogen for every 1 mole of oxygen. Since we have only 2 moles of oxygen, it will be completely consumed and we will only be able to form 4 moles of water, even though we have excess hydrogen.