Limiting reagent is the reactant which is used up completely in the reaction. Here, let’s find the way to identify it in basic concepts of Chemistry.
What is Limiting reagent ?
The reactant which is used up completely in the reaction is called L.R.
For example: A + B2 ➡️ AB2
a) If 2 mol of A reacts with 3 mol of B, then find out the LR.
2 moles of A will reacts completely with 2 moles of B. Hence, A is the L.R.
b) If 5 mol A + 2.5 mol B, then find the L.R. ?
2.5 moles of B will react with 2.5 moles of A. Hence, B is the L.R.
What is Excess reagent ?
The excess reagent is other than L.R. It is present in excess and not used up completely in the reaction.
A + B2 ➡️ AB2
a) If 2 mol of A reacts with 3 mol of B, then find out the LR.
B is present in excess. Hence, it is the excess reagent in this reaction.
b) If 5 mol A + 2.5 mol B, then find the L.R. ?
A is present in excess. Hence, it is the excess reagent in this reaction.
Identify the L.R. and E.R. in the following reaction ?
6H2 + 4 Cl2 ➡️ 8HCl + 2 H2
Answer : Cl2 is used up completely in the reaction. Hence, it is L.R. And H2 is the excess reagent. H2 molecule remains after the reaction. See the diagram below:
FAQ’s related to Limiting Reagent
- What is the difference between L.R. and E.R. ?
Answer : The reactant which is present in less amount is called L.R. The other reactant is excess reagent.
2. What is the difference between reactant and reagent ?
Answer : The substance is used up in the reaction is called reactant. The substance which starts the reaction is the reagent.
Here is the video on limiting agent
Check out the structure of NH3 here
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