Stoichiometry Module: Limiting Reactants
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If 200 g salicylic acid is added to 100 g acetic anhydride, which reactant will limit the reaction?

Step 3: Compare the needed amount to the amount actually present.

Moles of acetic anhydride needed Moles of acetic anhydride available
0.725 moles 0.980 moles

In this case, the 1.45 moles of salicylic acid requires 0.725 moles of acetic anhydride to react completely. There are 0.980 moles of acetic anhydride initially present.

What is the limiting reactant in this example?

Salicylic Acid Acetic Anhydride

Good! Since there is more than enough acetic anhydride to react with all of the salicylic acid, the salicylic acid will limit the reaction.

You can look at a more conceptual example by clicking on the s'more below.

If there is enough acetic anhydride to react will all of the salicylic acid, it will not limit the reaction. You should work through a more conceptual example of determining limiting reactants by clicking on the s'more below.