Let’s balance the chemical equation:
H₂O = H₂ + O₂
This means we start with water (H₂O) and break it into hydrogen gas (H₂) and oxygen gas (O₂). But right now, the number of atoms on each side doesn’t match — that’s why we need to balance it.
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Step 1: Count atoms on each side
Left side (reactant):
- H: 2 atoms (from H₂O)
- O: 1 atom (from H₂O)
Right side (products):
- H: 2 atoms (from H₂)
- O: 2 atoms (from O₂)
→ Hydrogen is balanced (2 on each side), but oxygen is NOT (1 on left, 2 on right).
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Step 2: Fix oxygen first
We have 1 oxygen on the left, but 2 on the right. So let’s put a
2 in front of H₂O to get 2 oxygens on the left:
2H₂O = H₂ + O₂
Now count again:
Left:
- H: 4 atoms (because 2 × H₂O → 2×2 = 4 H)
- O: 2 atoms (2 × 1 = 2)
Right:
- H: 2 atoms (still just H₂)
- O: 2 atoms (good!)
→ Oxygen is now balanced, but hydrogen is not (4 on left, 2 on right).
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Step 3: Fix hydrogen
We have 4 H on the left, so we need 4 H on the right. Since H₂ has 2 hydrogens per molecule, we need
2 molecules of H₂:
2H₂O = 2H₂ + O₂
Check again:
Left:
- H: 4 (2 × 2)
- O: 2 (2 × 1)
Right:
- H: 4 (2 × 2)
- O: 2 (1 × 2)
✔ Everything matches!
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Final Answer:
2H₂O = 2H₂ + O₂
Parent Tip: Review the logic above to help your child master the concept of equation for decomposition of water.
