Explain the concept of limiting reagent with a suitable example.

Q1. Limiting Reagent

Consider the reaction:

2H₂ + O₂ → 2H₂O

If 3 moles of H₂ react with 2 moles of O₂, which is the limiting reagent?

Step-by-Step Solution

Step 1: Balanced equation

2H₂ + O₂ → 2H₂O

Step 2: Required ratio

2 mol H₂ : 1 mol O₂

Step 3: Given quantities

H₂ = 3 mol
O₂ = 2 mol

For 3 mol H₂, oxygen required is:

O₂ required = 3 × 1/2 = 1.5 mol

But available O₂ = 2 mol. Therefore O₂ is in excess and H₂ is consumed first.

✅ Limiting Reagent = H₂