Limiting Reactants

A Delicious Cake

A Delicious Cake







Let’s revisit our amazing cake recipe one more time,

cake recipe

This recipe only makes one cake, however we know that if we want to make two cakes we would just need to double the recipe.

Now, consider this, If you double the amount of eggs in the recipe but left everything else the same how many cakes could you make? Well, if you had 2 cups of flour, 1 cup of sugar and 4 eggs, you could only make cake because you are limited by the amount of flour and sugar that you have.

cake recipe 2

According to this example we are able to use all of the flour and sugar that we have, however,  we are not able to use all 4 eggs. We will have 2 extra eggs left over, so we can say that eggs are in excess. Flour and sugar on the other hand will limit the number of cakes we can make so we can call flour and sugar the limiting ingredients.



Let’s see how this will relate to chemistry by looking at an example of a limiting reactant problem,

Propane undergoes a combustion reaction according the following balanced chemical equation, 

Propane Reaction

If 14. 3 g of propane reacts with 40.2 g of oxygen gas, 

     a) What is the limiting reactant?

     b) Which reactant is in excess?

     b) How many grams of water will be produced from this reaction?

     c) How many grams of excess reactant will be left over from this reaction?

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