📘 Stoichiometric Calculation
Stoichiometry deals with the quantitative relationship between reactants and products in a chemical reaction.
The given balanced chemical equation is:
1️⃣ Understand the Coefficients
The coefficients of the balanced equation represent the mole ratio of the substances.
Therefore:
- 2 moles H₂ react with 1 mole O₂.
- They produce 2 moles H₂O.
🎬 Molecular Stoichiometry Animation
2 molecules H₂ react with 1 molecule O₂.
2️⃣ Mole-to-Mole Calculation
Suppose we have 4 moles of H₂. How many moles of O₂ are required?
From the equation:
Therefore:
= 2 mol O₂
Thus, 4 moles of H₂ require 2 moles of O₂.
3️⃣ Mole-to-Mole Product Calculation
How much H₂O will be produced from 4 moles of H₂?
4 mol H₂ → 4 mol H₂O
4️⃣ Mass-to-Mass Stoichiometric Calculation
Let us calculate the mass of water produced when 4 g H₂ reacts completely with oxygen.
Molar mass:
H₂O = 18 g mol⁻¹
First calculate moles of H₂:
= 4 / 2
= 2 mol H₂
According to the equation:
Therefore:
= 36 g H₂O
5️⃣ Mass Relationship
The balanced equation:
Corresponding masses are:
1 mol O₂ = 1 × 32 = 32 g
2 mol H₂O = 2 × 18 = 36 g
4 g H₂ + 32 g O₂ → 36 g H₂O
📊 Stoichiometric Relationships
| Substance | Moles | Molar Mass | Mass |
|---|---|---|---|
| H₂ | 2 mol | 2 g/mol | 4 g |
| O₂ | 1 mol | 32 g/mol | 32 g |
| H₂O | 2 mol | 18 g/mol | 36 g |
🎯 General Method
Step 1: Write the balanced chemical equation.
Step 2: Convert the given quantity into moles.
Step 3: Use the mole ratio from the balanced equation.
Step 4: Convert the required moles into the desired unit.
Moles ↓
Mole Ratio ↓
Required Moles ↓
Required Quantity
✅ Key Result
2 mol H₂ + 1 mol O₂ → 2 mol H₂O
4 g H₂ + 32 g O₂ → 36 g H₂O
