Question

The reactant which is entirely consumed in the reaction is known as limiting
reagent. In the reaction $2A+4B\to 3C+4D$, when 5 moles of A react with 6
moles of B, then which is the limiting reagent and what would be the amount of C
formed respectively?
a.) C, 4.5 mol
b.) B, 4.5 mol
c.) B, 3.5 mol
d.) C, 4.0 mol

Answer 1

Limiting reagent in a chemical reaction limiting reagent is the reactant that is consumed first and prevents any further reaction from occurring, or reactant which is present in the lesser amount gets consumed after some time, and after that, no further reaction takes place whatever be the amount of the other reactant present.

Complete step by step answer:
$2A+4B\to 3C+4D$
Limiting reactant is declared which has the lowest ratio of $\dfrac{moles}{coefficient}$for reactant.
For A: $\dfrac{5}{2}=2.5$
For B: $\dfrac{6}{4}=1.5$
⇒B is limiting reagent here.
$2A+4B\to 3C+4D$
5 6
Here, 5 moles of A need 10 moles of B to react, thus B is a limiting agent.
3 moles of A can react with 6 moles of B, thus the no. of moles of C formed = $\dfrac{3}{2}\times 2=4.5$mol.
A factor is any quantitative boundary (for example an info) going into creating results (a yield) in a framework.
The amount of product formed during the reaction is determined by the limiting reagent.
For finding the limiting reagent we have to convert the given information into moles. Use stoichiometry for each individual reactant to find the mass of the product produced. The reactant that produces a lesser amount of product is the limiting reagent. The reactant that produces a larger amount of product is the excess reagent.
There can't be any limiting reagents in the equations. Equations are purely theoretical expressions and are always balanced in terms of moles. "Limiting reagents" arise in real-world chemical reactions.
So, the correct answer is “Option A”.

Note: If there is only one reagent would be used up 'first' and would limit the amount of product, then it is a limiting reagent. One way to determine limiting reagent is to compare the mole ratio of reactants used. This method is useful when there are only two reactants.