(solved)Question 1.23 of NCERT Class XI Chemistry Chapter 1

In a reaction A + B2 → AB2 Identify the limiting reagent, if any, in the following reaction mixtures. (i) 300 atoms of A + 200 molecules of B (ii) 2 mol A + 3 mol B (iii) 100 atoms of A + 100 molecules of B (iv) 5 mol A + 2.5 mol B (v) 2.5 mol A + 5 mol B

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Parveen,

Question 1.23
NCERT Class XI Chemistry

In a reaction A + B2 → AB2 Identify the limiting reagent, if any, in the following reaction mixtures. (i) 300 atoms of A + 200 molecules of B (ii) 2 mol A + 3 mol B (iii) 100 atoms of A + 100 molecules of B (iv) 5 mol A + 2.5 mol B (v) 2.5 mol A + 5 mol B

Solution in Detail

The given equation is already balanced.

Def. of Limiting Reagant [has marks]: the reactant that gets consumed first is called the limiting reagent. [refer the book for the definition]

$\displaystyle \underline{\text{Part (i)}}$

1 atom of A combines with 1 molecule of B

So, 300 of A will combine with 300 of B

But B is only 200 molecules (smaller amount). Hence B will be the limiting reagant.

$\displaystyle \underline{\text{Part (ii)}}$

1 mol of A combines with 1 mol of B

So, 2 mol of A will combine with 2 mol of B

But B is 3 mol (larger amount). Hence A will be the limiting reagant.

$\displaystyle \underline{\text{Part (iii)}}$

1 atom of A combines with 1 molecule of B

So, 100 of A will combine with 100 of B

Both get consumed. So there is no limiting reagant.

$\displaystyle \underline{\text{Part (iv)}}$

1 mol of A combines with 1 mol of B

So, 5 mol of A will combine with 5 mol of B

But B is 2.5 mol (smaller amount). Hence B will be the limiting reagant.

$\displaystyle \underline{\text{Part (v)}}$

1 mol of A combines with 1 mol of B

So, 2.5 mol of A will combine with 2.5 mol of B

But B is 5 mol (larger amount). Hence A will be the limiting reagant.

Video Explanation
(detailed solution given after this video)

Please watch this youtube video for a quick explanation of the solution:

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