If you are given a chemical equation and specific amounts for each reactant in grams, how do you determine the maximum amount of product that can be made?
In a chemical reaction, the determination of amount of product formed is also known as the determination of the limiting reagent. The other reactants are sometimes referred to as being in excess, since there will be some leftover after the limiting reagent is completely used up.
The maximum amount of product formed can be determined by the following example.
For the following reaction, what is the limiting reagent if we start with 2.80g of Al and 4.25g of Cl2?
First, let’s check if our reaction is balanced: The above equation is well balanced with 2 Al atoms and 6 Cl atoms on the both side (in reactant and product). In this problem, we know the mass of both reactants, and we would like to know which one will get used up first. So in the next step, we will convert everything to moles, and then we will use the stoichiometric ratio from the balanced reaction to find the limiting reagent.