The other reactants are partially consumed where the remaining amount is considered "in excess".
This example problem demonstrates a method to determine the limiting reactant of a chemical reaction.
Hopefully, you didn't have too much trouble figuring out that we can make only five glasses of ice water.
Let's go through this calculation carefully to see what we did (it'll be clear why we need to do this in a second).
The water is called the excess reactant because we had more of it than was needed.
We can use this method in stoichiometry calculations.Next, to find the amount of excess reactant, we must calculate how much of the non-limiting reactant (oxygen) actually did react with the limiting reactant (ammonia). 1.70 g is the amount of ammonia that reacted, not what is left over.To find the amount of excess reactant remaining, subtract the amount that reacted from the amount in the original sample.In our example, we would say that ice is the limiting reactant.The ice is said to be "limiting" because it is the ingredient we would run out of first, which puts a limit on how much ice water we can make.One reactant will be completely used up before the others.The reactant used up first is known as the limiting reactant.The excess reactant remains because there is nothing with which it can react.No matter how many tires there are, if there are only 8 car bodies, then only 8 cars can be made.The first stoichiometry calculation will be performed using "1.75 mol O2" as our starting point, and the second will be performed using "2.75 mol H" is the smaller of these two answers, it is the amount of water that we can actually make.The limiting reactant is hydrogen because it is the reactant that limits the amount of water that can be formed since there is less of it than oxygen.