The image presents a chemical reaction and applies the
Law of Conservation of Mass, which states that
mass is neither created nor destroyed in a chemical reaction. This means the total mass of the reactants must equal the total mass of the products.
---
🔬 Given Reaction:
\[
\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}
\]
📊 Masses Provided:
-
CH₄ (methane): 16 g
-
2O₂ (oxygen gas): 64 g
-
CO₂ (carbon dioxide): 44 g
-
2H₂O (water): ? (unknown)
---
✔ Step-by-step Solution:
#### 1.
Total mass of reactants:
\[
\text{Mass of CH}_4 + \text{Mass of O}_2 = 16\,\text{g} + 64\,\text{g} = 80\,\text{g}
\]
#### 2.
Total mass of products must also be 80 g (by conservation of mass):
\[
\text{Mass of CO}_2 + \text{Mass of H}_2\text{O} = 80\,\text{g}
\]
We know:
- CO₂ = 44 g
- So, mass of water (H₂O) = ?
\[
\text{Mass of H}_2\text{O} = 80\,\text{g} - 44\,\text{g} = 36\,\text{g}
\]
---
✔ Final Answer:
The missing mass of water (
2H₂O) is
36 grams.
> 💡 Note: The image shows "80g" on both sides — this is correct for the
total mass. But the
individual mass of water is
not 80g, it's
36g.
---
✔ Verification:
Let’s check the molar masses to confirm:
- CH₄: 12 + 4(1) = 16 g/mol → 16 g ✔️
- O₂: 32 g/mol → 2 mol = 64 g ✔️
- CO₂: 12 + 32 = 44 g/mol → 44 g ✔️
- H₂O: 18 g/mol → 2 mol = 36 g ✔️
Total reactants: 16 + 64 = 80 g
Total products: 44 + 36 = 80 g →
Balanced!
---
✔ Conclusion:
The
mass of water produced is 36 grams, and the total mass is conserved at
80 grams on both sides.
> 🟩 Correct answer:
36 g (for water), not 80 g. The 80 g refers to the
total mass, not the water alone.
Parent Tip: Review the logic above to help your child master the concept of conservation of mass problems.
