Print and digital worksheets for balancing chemical equations, featuring practice problems and review questions.

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Let’s go through each equation shown, balance them, and then explain the process step by step. Here are the equations from the worksheets:

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🔬 1. NH₃ → N₂ + H₂

This is a decomposition reaction.

Unbalanced:
```
NH₃ → N₂ + H₂
```

Step-by-step balancing:

- Left side: 1 N, 3 H
- Right side: 2 N, 2 H

We need to balance N and H.

- To get 2 N on both sides: Use 2 NH₃ → gives 2 N and 6 H.
- On the right: N₂ has 2 N → good.
- H₂ needs to account for 6 H → so use 3 H₂.

✔ Balanced:
```
2 NH₃ → N₂ + 3 H₂
```

Atom count:
- N: 2 = 2 ✔
- H: 6 = 6 ✔

---

🔬 2. NO₂ → NO + O₂

Decomposition of nitrogen dioxide.

Unbalanced:
```
NO₂ → NO + O₂
```

- Left: 1 N, 2 O
- Right: 1 N, 1 O (in NO) + 2 O (in O₂) = 3 O → not balanced

Try using coefficients:

- Try 2 NO₂ → 2 N, 4 O
- Right: 2 NO → 2 N, 2 O; O₂ → 2 O → total 4 O

✔ Balanced:
```
2 NO₂ → 2 NO + O₂
```

Check:
- N: 2 = 2 ✔
- O: 4 = 2 + 2 = 4 ✔

---

🔬 3. P₄ + H₂ → PH₃

Reaction of white phosphorus with hydrogen.

Unbalanced:
```
P₄ + H₂ → PH₃
```

- Left: 4 P, 2 H
- Right: 1 P, 3 H

Need to balance P and H.

- Use P₄ → makes 4 P → need 4 PH₃
- 4 PH₃ → 4 P, 12 H → need 6 H₂ (since H₂ gives 2 H per molecule)

✔ Balanced:
```
P₄ + 6 H₂ → 4 PH₃
```

Check:
- P: 4 = 4 ✔
- H: 12 = 12 ✔

---

🔬 4. CH₃OH → CO + H₂

Methanol decomposition.

Unbalanced:
```
CH₃OH → CO + H₂
```

- Left: 1 C, 4 H, 1 O
- Right: 1 C, 1 O, 2 H (in H₂)

H atoms don’t match.

Try:
- CH₃OH → CO + 2 H₂ → H: left = 4, right = 4

✔ Balanced:
```
CH₃OH → CO + 2 H₂
```

Check:
- C: 1 = 1 ✔
- O: 1 = 1 ✔
- H: 4 = 4 ✔

---

🔬 5. C + H₂O → CH₄ + CO₂

Carbon reacts with steam.

Wait — this one might be miswritten. Usually, carbon reacts with steam to form CO and H₂, but here it shows CH₄ and CO₂.

But let's try to balance as written:

Unbalanced:
```
C + H₂O → CH₄ + CO₂
```

Left: 1 C, 2 H, 1 O
Right: 1 C (in CH₄), 4 H, 1 C (in CO₂), 2 O → total: 2 C, 4 H, 2 O

So we need more C and H₂O.

Try:
- 2 C + 2 H₂O → CH₄ + CO₂

Now check:
- Left: 2 C, 4 H, 2 O
- Right: 1 C (CH₄) + 1 C (CO₂) = 2 C; 4 H; 2 O

✔ Balanced:
```
2 C + 2 H₂O → CH₄ + CO₂
```

But this isn't a typical reaction. More commonly, it's:
```
C + H₂O → CO + H₂
```
But if this is the intended equation, then it works.

---

🔬 6. CH₄ + O₂ → CO₂ + H₂O

Combustion of methane.

Unbalanced:
```
CH₄ + O₂ → CO₂ + H₂O
```

- Left: 1 C, 4 H, 2 O
- Right: 1 C, 2 O (CO₂) + 1 O (H₂O) = 3 O, 2 H → not balanced

Balance:
- Carbon: already 1:1
- Hydrogen: 4 H → need 2 H₂O → gives 4 H
- Oxygen: now 2 H₂O = 2 O, CO₂ = 2 O → total 4 O
- So need 2 O₂ → gives 4 O

✔ Balanced:
```
CH₄ + 2 O₂ → CO₂ + 2 H₂O
```

Check:
- C: 1 = 1 ✔
- H: 4 = 4 ✔
- O: 4 = 2 + 2 = 4 ✔

---

🔬 7. CH₄ + H₂O → H₂ + CO

Steam reforming of methane.

Unbalanced:
```
CH₄ + H₂O → H₂ + CO
```

- Left: 1 C, 4 H, 2 H, 1 O → total: 1 C, 6 H, 1 O
- Right: 2 H (H₂), 1 C, 1 O → H only 2

Not balanced.

Try:
- CH₄ + H₂O → 3 H₂ + CO

Now:
- Left: C=1, H=4+2=6, O=1
- Right: C=1, O=1, H=6

✔ Balanced:
```
CH₄ + H₂O → 3 H₂ + CO
```

Check:
- C: 1 = 1 ✔
- H: 6 = 6 ✔
- O: 1 = 1 ✔

---

🔬 8. C₂H₆ + Cl₂ → C₂H₅Cl + HCl

Chlorination of ethane.

Unbalanced:
```
C₂H₆ + Cl₂ → C₂H₅Cl + HCl
```

- Left: 2 C, 6 H, 2 Cl
- Right: 2 C, 5 H (C₂H₅Cl), 1 H (HCl) = 6 H, 1 Cl (C₂H₅Cl) + 1 Cl (HCl) = 2 Cl

✔ Already balanced!

```
C₂H₆ + Cl₂ → C₂H₅Cl + HCl
```

Check:
- C: 2 = 2 ✔
- H: 6 = 6 ✔
- Cl: 2 = 2 ✔

---

🔬 9. CS₂ + O₂ → CO₂ + SO₂

Combustion of carbon disulfide.

Unbalanced:
```
CS₂ + O₂ → CO₂ + SO₂
```

- Left: 1 C, 2 S, 2 O
- Right: 1 C, 2 O (CO₂), 1 S, 2 O (SO₂) → total: 1 C, 1 S, 4 O → not balanced

Need:
- 2 SO₂ → 2 S, 4 O
- CO₂ → 1 C, 2 O
- Total O: 2 (CO₂) + 4 (SO₂) = 6 O → need 3 O₂

So:
- CS₂ + 3 O₂ → CO₂ + 2 SO₂

✔ Balanced:
```
CS₂ + 3 O₂ → CO₂ + 2 SO₂
```

Check:
- C: 1 = 1 ✔
- S: 2 = 2 ✔
- O: 6 = 2 + 4 = 6 ✔

---

🔬 10. SO₂ + H₂ → S + H₂O

Reduction of sulfur dioxide.

Unbalanced:
```
SO₂ + H₂ → S + H₂O
```

- Left: 1 S, 2 O, 2 H
- Right: 1 S, 2 H, 1 O → O missing

Need 2 H₂O → 2 O, 4 H → so need 2 H₂

Try:
- SO₂ + 2 H₂ → S + 2 H₂O

✔ Balanced:
```
SO₂ + 2 H₂ → S + 2 H₂O
```

Check:
- S: 1 = 1 ✔
- O: 2 = 2 ✔
- H: 4 = 4 ✔

---

🔬 11. C₂H₂ + O₂ → CO₂ + H₂O

Combustion of acetylene.

Unbalanced:
```
C₂H₂ + O₂ → CO₂ + H₂O
```

- Left: 2 C, 2 H, 2 O
- Right: 1 C, 2 O (CO₂), 2 H, 1 O (H₂O) → total: 1 C, 2 H, 3 O

Balance:
- 2 CO₂ → 2 C, 4 O
- 1 H₂O → 2 H → but we have 2 H → OK
- But H₂O should be 1? Wait: C₂H₂ has 2 H → need 1 H₂O → but that gives only 2 H → OK
- But O: 2 CO₂ = 4 O, H₂O = 1 O → total 5 O → need 5/2 O₂

Use fractions:
- C₂H₂ + 5/2 O₂ → 2 CO₂ + H₂O

Multiply all by 2:
- 2 C₂H₂ + 5 O₂ → 4 CO₂ + 2 H₂O

✔ Balanced:
```
2 C₂H₂ + 5 O₂ → 4 CO₂ + 2 H₂O
```

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

---

🔬 12. NH₃ + O₂ → N₂ + H₂O

Ammonia oxidation.

Unbalanced:
```
NH₃ + O₂ → N₂ + H₂O
```

- Left: 1 N, 3 H, 2 O
- Right: 2 N, 2 H, 1 O → not balanced

Balance N: 2 NH₃ → 2 N
- H: 6 H → need 3 H₂O → 3 H₂O → 3 O
- O: 3 O → need 3/2 O₂

So:
- 2 NH₃ + 3/2 O₂ → N₂ + 3 H₂O

Multiply by 2:
- 4 NH₃ + 3 O₂ → 2 N₂ + 6 H₂O

✔ Balanced:
```
4 NH₃ + 3 O₂ → 2 N₂ + 6 H₂O
```

Check:
- N: 4 = 4 ✔
- H: 12 = 12 ✔
- O: 6 = 6 ✔

---

🔬 13. NO₂ + H₂O → NH₃ + O₂

This one is tricky. Let's check.

Unbalanced:
```
NO₂ + H₂O → NH₃ + O₂
```

- Left: 1 N, 2 O, 2 H, 1 O → total: 1 N, 3 O, 2 H
- Right: 1 N, 3 H, 2 O → H and O mismatch

Try balancing:
- Need 2 NO₂ → 2 N, 4 O
- H₂O → 2 H, 1 O → total: 2 N, 5 O, 2 H
- Right: 2 NH₃ → 2 N, 6 H → need 3 H₂O → 6 H, 3 O → total H: 6, O: 3
- But left: 2 NO₂ + 3 H₂O → 2 N, 4 O + 3 O = 7 O, 6 H
- Right: 2 NH₃ + ? O₂ → 2 N, 6 H, and O₂ → say 2 O₂ → 4 O → total O: 4 → too little

This reaction doesn't typically happen. It may be a mistake.

Alternatively, the correct reaction is:
```
4 NO₂ + 6 H₂O → 4 NH₃ + 7 O₂
```

But that's not balanced.

Actually, NO₂ doesn't react with water to form NH₃ and O₂. It forms HNO₃ and NO.

So likely, this is a misleading or incorrect equation.

Better to skip or note: Not a valid reaction under normal conditions.

---

🔬 14. CO₂ + H₂O → C₂H₅OH + O₂

This is photosynthesis backward? But ethanol from CO₂ and H₂O?

Not spontaneous.

But let's balance:

Unbalanced:
```
CO₂ + H₂O → C₂H₅OH + O₂
```

- Left: 1 C, 2 O, 2 H, 1 O → total: 1 C, 3 O, 2 H
- Right: 2 C, 6 H, 1 O (in ethanol) + 2 O (in O₂) → 3 O

So need:
- 2 CO₂ → 2 C, 4 O
- 3 H₂O → 6 H, 3 O → total: 2 C, 6 H, 7 O
- Right: C₂H₅OH → 2 C, 6 H, 1 O; O₂ → 2 O → total: 3 O → not enough

Try:
- 2 CO₂ + 3 H₂O → C₂H₅OH + 3 O₂

Now:
- Left: 2 C, 6 H, 7 O
- Right: 2 C, 6 H, 1 O + 6 O = 7 O → yes!

✔ Balanced:
```
2 CO₂ + 3 H₂O → C₂H₅OH + 3 O₂
```

But this is not thermodynamically favorable — it's reverse of fermentation.

Still, mathematically balanced.

---

## ✔ Summary of Balanced Equations:

| Equation | Balanced Form |
|--------|----------------|
| 1. NH₃ → N₂ + H₂ | 2 NH₃ → N₂ + 3 H₂ |
| 2. NO₂ → NO + O₂ | 2 NO₂ → 2 NO + O₂ |
| 3. P₄ + H₂ → PH₃ | P₄ + 6 H₂ → 4 PH₃ |
| 4. CH₃OH → CO + H₂ | CH₃OH → CO + 2 H₂ |
| 5. C + H₂O → CH₄ + CO₂ | 2 C + 2 H₂O → CH₄ + CO₂ |
| 6. CH₄ + O₂ → CO₂ + H₂O | CH₄ + 2 O₂ → CO₂ + 2 H₂O |
| 7. CH₄ + H₂O → H₂ + CO | CH₄ + H₂O → 3 H₂ + CO |
| 8. C₂H₆ + Cl₂ → C₂H₅Cl + HCl | C₂H₆ + Cl₂ → C₂H₅Cl + HCl |
| 9. CS₂ + O₂ → CO₂ + SO₂ | CS₂ + 3 O₂ → CO₂ + 2 SO₂ |
| 10. SO₂ + H₂ → S + H₂O | SO₂ + 2 H₂ → S + 2 H₂O |
| 11. C₂H₂ + O₂ → CO₂ + H₂O | 2 C₂H₂ + 5 O₂ → 4 CO₂ + 2 H₂O |
| 12. NH₃ + O₂ → N₂ + H₂O | 4 NH₃ + 3 O₂ → 2 N₂ + 6 H₂O |
| 13. NO₂ + H₂O → NH₃ + O₂ | Not a valid reaction (likely error) |
| 14. CO₂ + H₂O → C₂H₅OH + O₂ | 2 CO₂ + 3 H₂O → C₂H₅OH + 3 O₂ |

---

## 🧠 How to Balance Chemical Equations: Steps

1. Write the unbalanced equation.
2. Count atoms of each element on both sides.
3. Start with elements that appear in only one compound on each side.
4. Use coefficients (whole numbers) to balance atoms.
5. Never change subscripts (that changes the compound).
6. Check all atoms again.
7. Simplify coefficients if possible (lowest whole numbers).

---

## 💡 Review Questions (from the worksheet):

1. What does the Law of Conservation of Mass say?

> Matter cannot be created or destroyed in a chemical reaction. The number of atoms of each element must be the same on both sides of the equation.

2. How does it help solve chemical equations?

> It means we must balance the equation so atoms are conserved — no atoms lost or gained.

3. What is a chemical reaction?

> A process where substances (reactants) are transformed into new substances (products) with different properties.

4. Difference between atom and molecule?

> An atom is the smallest unit of an element. A molecule is two or more atoms chemically bonded together.

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