Question

How does a limiting reagent affect the products in a chemical reaction?

Answer 1

In a reaction when a reactant limits the amount of product that can be formed is called limiting reagent. When a limiting reagent is consumed in a reaction the reaction will stop. There is another term called an excess reactant, which states about the remaining reactant that is left after a complete chemical reaction.

Complete step by step answer:
The reactant which gets consumed and the further reaction does not happen this is due to the limiting reagents. The compound which gets consumed in a reaction i.e., the limiting reagent. When the limiting reagent is consumed entirely and the amount of product is formed is called theoretical yield. The limiting reagent will reduce the amount of product formed. The reactant which is left excess reagent is left it won’t further products. So, the reaction depends on the limiting reagent.

Let’s understand with a simple example, suppose if you want to prepare masala dosa. You have one bowl of masala and a tub of batter. So, here the masala will act as a limiting reagent. And you can only serve that masala dosa until the masala gets consumed completely. After that, there won’t be any masala dosa that will be served.

Let’s consider one more example;
$3{H_2}\, + \,{N_2}\, \to \,2N{H_3}$
Suppose, if you have $10$ molecules of ${H_2}$ and $5$ molecules of ${N_2}$. You need $3$ molecules of ${H_2}$ for every $1$ molecule of ${N_2}$. $5\,molecules\,{N_2}\, \times \,\dfrac{{3\,molecules\,of\,{H_2}}}{{1\,molecules\,of\,{N_2}}}\, = 15\,molecules\,of\,{H_2}$
Here, hydrogen is insufficient so the limiting reagent will be hydrogen.

Note: There are many ways to determine the limiting reagent, one of the famous methods is from mole ratios from the balanced equation. When one mole of nitrogen requires three moles of hydrogen to form two moles of ammonia. We observe here that mole ratios are helping to decide if we have an insufficient amount of one reactant.