Question

What is the limiting reactant?

Answer 1

Limiting reactant:

• The reactant which is present in the least amount gets consumed after some time and after that further reaction does not take place whatever the amount of the other reactant.
• Hence, the reactant, which gets consumed first, limits the amount of product formed and is, therefore, called the limiting reactant.

Example

${\mathrm{N}}_2\left(\mathrm{g}\right)+3{\mathrm{H}}_2\left(\mathrm{g}\right)\to 2{\mathrm{NH}}_3\left(\mathrm{g}\right)$

• In the reaction given above, 3 moles of Hydrogen gas are required to react with 1 mole of nitrogen gas to form 2 moles of ammonia.
• But what if, during the reaction, only 2 moles of hydrogen gas are available along with 1 mole of nitrogen.
• In that case, the entire quantity of nitrogen cannot be used (because the entirety of nitrogen requires 3 moles of hydrogen gas to react). Hence, the hydrogen gas is limiting the reaction and is therefore called the limiting reagent for this reaction.