49 Balancing Chemical Equations Worksheets [with Answers] - Free Printable

Let's solve each of these chemical equations by balancing them. Balancing a chemical equation means ensuring that the number of atoms of each element is the same on both sides (reactants and products), following the Law of Conservation of Mass.

We'll go through each one step-by-step, showing the balanced equation and explaining the logic.

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1. N₂ + H₂ → NH₃

- Nitrogen: 2 on left, 1 in NH₃ → need 2 NH₃
- Hydrogen: 2 H₂ = 4 H atoms; 2 NH₃ has 6 H → need 3 H₂

Balanced:
> N₂ + 3H₂ → 2NH₃

✔ Check:
N: 2 = 2
H: 6 = 6

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2. S₈ + O₂ → SO₃

- S₈ has 8 S atoms → need 8 SO₃
- Each SO₃ has 3 O → 8 SO₃ needs 24 O atoms → 12 O₂ molecules

Balanced:
> S₈ + 12O₂ → 8SO₃

✔ Check:
S: 8 = 8
O: 24 = 24

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3. HgO → Hg + O₂

- HgO has 1 Hg and 1 O per molecule
- O₂ is diatomic → need even number of O atoms

So, 2 HgO → 2 Hg + O₂

Balanced:
> 2HgO → 2Hg + O₂

✔ Check:
Hg: 2 = 2
O: 2 = 2

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4. Zn + HCl → ZnCl₂ + H₂

- ZnCl₂ has 2 Cl → need 2 HCl
- H₂ comes from 2 H → so 2 HCl gives 2 H

Balanced:
> Zn + 2HCl → ZnCl₂ + H₂

✔ Check:
Zn: 1 = 1
H: 2 = 2
Cl: 2 = 2

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5. SiCl₄ + H₂O → H₄SiO₄ + HCl

- Si: 1 = 1
- Cl: 4 on left → need 4 HCl on right
- H: H₂O has 2 H, H₄SiO₄ has 4 H → total H on right: 4 (from H₄SiO₄) + 4 (from HCl) = 8 H
- So need 4 H₂O (8 H)

Now check O: 4 H₂O → 4 O, H₄SiO₄ has 4 O → good

Balanced:
> SiCl₄ + 4H₂O → H₄SiO₄ + 4HCl

✔ Check:
Si: 1 = 1
Cl: 4 = 4
H: 8 = 4+4
O: 4 = 4

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6. Na + H₂O → NaOH + H₂

- Na: 1 = 1
- H₂O has 2 H → NaOH has 1 H, H₂ has 2 H → need to balance H
- Try 2Na → 2NaOH → 2 Na, 2 H in NaOH, plus H₂ → total 4 H needed
- So need 2 H₂O → 4 H

Try:
> 2Na + 2H₂O → 2NaOH + H₂

Check:
Na: 2 = 2
H: 4 = 2 (in NaOH) + 2 (in H₂) = 4
O: 2 = 2

✔ Balanced!

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7. H₃PO₄ → H₄P₂O₇ + H₂O

- Left: H₃PO₄ → 3 H, 1 P, 4 O
- Right: H₄P₂O₇ has 2 P → need 2 H₃PO₄
- 2 H₃PO₄ → 6 H, 2 P, 8 O
- H₄P₂O₇ has 4 H, 2 P, 7 O → leaves 2 H and 1 O → form H₂O

So:
> 2H₃PO₄ → H₄P₂O₇ + H₂O

✔ Check:
H: 6 = 4 + 2
P: 2 = 2
O: 8 = 7 + 1

✔️ Balanced

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8. Si₂H₆ + O₂ → SiO₂ + H₂O

- Si₂H₆ → 2 Si, 6 H
- Need 2 SiO₂ → 2 Si, 4 O
- H₂O: 6 H → 3 H₂O → 3 O
- Total O needed: 4 (from SiO₂) + 3 (from H₂O) = 7 O → but O₂ is diatomic → need 3.5 O₂ → not allowed

Use whole numbers: multiply entire equation by 2

Start over:
- 2 Si₂H₆ → 4 Si, 12 H
- → 4 SiO₂ → 4 Si, 8 O
- 12 H → 6 H₂O → 6 O
- Total O: 8 + 6 = 14 → need 7 O₂

So:
> 2Si₂H₆ + 7O₂ → 4SiO₂ + 6H₂O

✔ Check:
Si: 4 = 4
H: 12 = 12
O: 14 = 8 + 6 = 14

✔️ Balanced

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9. Al(OH)₃ + H₂SO₄ → Al₂(SO₄)₃ + H₂O

- Al: 2 in Al₂(SO₄)₃ → need 2 Al(OH)₃
- SO₄: 3 in Al₂(SO₄)₃ → need 3 H₂SO₄
- Now look at H and O

Left:
- 2 Al(OH)₃ → 2 Al, 6 O, 6 H
- 3 H₂SO₄ → 6 H, 3 S, 12 O → total H: 6 + 6 = 12, O: 6 + 12 = 18

Right:
- Al₂(SO₄)₃ → 2 Al, 3 S, 12 O
- H₂O → need 12 H → 6 H₂O → 6 O

Total O on right: 12 + 6 = 18 → matches

So:
> 2Al(OH)₃ + 3H₂SO₄ → Al₂(SO₄)₃ + 6H₂O

✔ Check:
Al: 2 = 2
S: 3 = 3
O: 6 + 12 = 18 → 12 + 6 = 18
H: 6 + 6 = 12 → 12

✔️ Balanced

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10. Fe + O₂ → Fe₂O₃

- Fe₂O₃ has 2 Fe → need 2 Fe
- O₂ has 2 O, Fe₂O₃ has 3 O → LCM of 2 and 3 is 6

So:
- 2 Fe₂O₃ → 4 Fe, 6 O
- Need 3 O₂ → 6 O
- Need 4 Fe

So:
> 4Fe + 3O₂ → 2Fe₂O₃

✔ Check:
Fe: 4 = 4
O: 6 = 6

✔️ Balanced

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11. Fe₂(SO₄)₃ + KOH → K₂SO₄ + Fe(OH)₃

- Fe₂(SO₄)₃ → 2 Fe, 3 SO₄
- SO₄ → need 3 K₂SO₄ → 6 K
- So need 6 KOH → 6 K, 6 OH
- Fe: 2 → need 2 Fe(OH)₃ → 6 OH → matches

Now check:
Left:
- Fe₂(SO₄)₃ → 2 Fe, 3 S, 12 O
- 6 KOH → 6 K, 6 O, 6 H

Total: 2 Fe, 3 S, 18 O, 6 K, 6 H

Right:
- 3 K₂SO₄ → 6 K, 3 S, 12 O
- 2 Fe(OH)₃ → 2 Fe, 6 O, 6 H

Total: 2 Fe, 3 S, 18 O, 6 K, 6 H → ✔

Balanced:
> Fe₂(SO₄)₃ + 6KOH → 3K₂SO₄ + 2Fe(OH)₃

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12. FeS₂ + O₂ → Fe₂O₃ + SO₂

- Fe: 2 in Fe₂O₃ → need 2 FeS₂
- S: 2 × 2 = 4 S → need 4 SO₂
- O: Fe₂O₃ → 3 O, 4 SO₂ → 8 O → total 11 O → need 11/2 O₂ → not integer

Multiply by 2:

→ 4 FeS₂ → 4 Fe, 8 S
→ 2 Fe₂O₃ → 4 Fe, 6 O
→ 8 SO₂ → 8 S, 16 O
Total O needed: 6 + 16 = 22 → 11 O₂

So:
> 4FeS₂ + 11O₂ → 2Fe₂O₃ + 8SO₂

✔ Check:
Fe: 4 = 4
S: 8 = 8
O: 22 = 6 + 16 = 22

✔️ Balanced

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13. Al + FeO → Al₂O₃ + Fe

- Al₂O₃ → 2 Al, 3 O
- FeO → 1 Fe, 1 O → need 3 FeO for 3 O
- So: 3 FeO → 3 Fe, 3 O
- Al₂O₃ → 2 Al → need 2 Al

So:
> 2Al + 3FeO → Al₂O₃ + 3Fe

✔ Check:
Al: 2 = 2
Fe: 3 = 3
O: 3 = 3

✔️ Balanced

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14. Na₂CO₃ + HCl → NaCl + H₂O + CO₂

- Na₂CO₃ → 2 Na, 1 C, 3 O
- CO₂ → 1 C, 2 O → good
- H₂O → 1 O, 2 H
- HCl → H and Cl
- NaCl → 2 Na → need 2 NaCl → 2 Cl → 2 HCl

So:
- 2 HCl → 2 H, 2 Cl
- H₂O → needs 2 H → perfect

So:
> Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂

✔ Check:
Na: 2 = 2
C: 1 = 1
O: 3 = 1 (H₂O) + 2 (CO₂) = 3
H: 2 = 2
Cl: 2 = 2

✔️ Balanced

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15. K + Br₂ → KBr

- Br₂ → 2 Br → need 2 KBr → 2 K
- So:
> 2K + Br₂ → 2KBr

✔ Check:
K: 2 = 2
Br: 2 = 2

✔️ Balanced

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16. P₄ + O₂ → P₂O₅

- P₄ → 4 P → need 2 P₂O₅ → 4 P, 10 O
- O₂ → 10 O → need 5 O₂

So:
> P₄ + 5O₂ → 2P₂O₅

✔ Check:
P: 4 = 4
O: 10 = 10

✔️ Balanced

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17. C₂H₂ + O₂ → CO₂ + H₂O

- C₂H₂ → 2 C, 2 H
- CO₂ → 2 C → need 2 CO₂
- H₂O → 2 H → need 1 H₂O

But O:
- 2 CO₂ → 4 O
- 1 H₂O → 1 O → total 5 O → need 5/2 O₂ → not integer

Multiply by 2:

→ 2 C₂H₂ → 4 C, 4 H
→ 4 CO₂ → 4 C, 8 O
→ 2 H₂O → 4 H, 2 O → total O: 10 → need 5 O₂

So:
> 2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O

✔ Check:
C: 4 = 4
H: 4 = 4
O: 10 = 8 + 2 = 10

✔️ Balanced

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## ✔ Final Answer: All Balanced Equations

1. N₂ + 3H₂ → 2NH₃
2. S₈ + 12O₂ → 8SO₃
3. 2HgO → 2Hg + O₂
4. Zn + 2HCl → ZnCl₂ + H₂
5. SiCl₄ + 4H₂O → H₄SiO₄ + 4HCl
6. 2Na + 2H₂O → 2NaOH + H₂
7. 2H₃PO₄ → H₄P₂O₇ + H₂O
8. 2Si₂H₆ + 7O₂ → 4SiO₂ + 6H₂O
9. 2Al(OH)₃ + 3H₂SO₄ → Al₂(SO₄)₃ + 6H₂O
10. 4Fe + 3O₂ → 2Fe₂O₃
11. Fe₂(SO₄)₃ + 6KOH → 3K₂SO₄ + 2Fe(OH)₃
12. 4FeS₂ + 11O₂ → 2Fe₂O₃ + 8SO₂
13. 2Al + 3FeO → Al₂O₃ + 3Fe
14. Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
15. 2K + Br₂ → 2KBr
16. P₄ + 5O₂ → 2P₂O₅
17. 2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O

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