Balancing Chemical Reactions Worksheet for 9th - 11th Grade ... - Free Printable

Let’s go step by step to balance each chemical equation and identify the type of reaction.

We’ll use these common reaction types:
- Synthesis: A + B → AB (two or more substances combine)
- Decomposition: AB → A + B (one substance breaks down)
- Single Replacement: A + BC → AC + B (element replaces another in a compound)
- Double Replacement: AB + CD → AD + CB (ions swap partners)
- Combustion: Fuel + O₂ → CO₂ + H₂O (usually involves oxygen, produces heat/light)

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1. Cl₂ + 2 NaBr → Br₂ + 2 NaCl

Already balanced? Let’s check:

Left: Cl=2, Na=2, Br=2
Right: Br=2, Na=2, Cl=2 → ✔ Balanced

Type: Chlorine replaces bromine in sodium bromide → Single Replacement

Name: Single Replacement

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2. 2 Al + Fe₂O₃ → Al₂O₃ + 2 Fe

Check atoms:

Left: Al=2, Fe=2, O=3
Right: Al=2, O=3, Fe=2 → ✔ Balanced

Type: Aluminum replaces iron in iron oxide → Single Replacement

Name: Single Replacement

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3. Pb(NO₃)₂ + 2 KI → PbI₂ + 2 KNO₃

Wait — original says: _Pb_ + _KI_ → _PbI₂_ + _KNO₃_

That can’t be right as written. Probably meant:

Pb(NO₃)₂ + 2 KI → PbI₂ + 2 KNO₃

But since the problem shows “_Pb_ + _KI_”, maybe it's a typo? Looking at products: PbI₂ and KNO₃ — so reactants must include nitrate.

Actually, looking again — perhaps it’s:

Pb(NO₃)₂ + 2 KI → PbI₂ + 2 KNO₃

But the worksheet has blanks for coefficients only on given formulas.

Original line:
_ Pb + _ KI → _ PbI₂ + _ KNO₃ ← This is chemically incorrect because Pb alone won’t make KNO₃.

Wait — likely it’s supposed to be:

Pb(NO₃)₂ + 2 KI → PbI₂ + 2 KNO₃

But since the problem writes “Pb” not “Pb(NO₃)₂”, this might be an error. However, in many worksheets, they sometimes write shorthand.

Alternatively, maybe it’s:

Pb + 2 KI → PbI₂ + 2 K — but that doesn’t match product KNO₃.

This seems like a mistake in the problem. But let’s assume it’s:

Pb(NO₃)₂ + 2 KI → PbI₂ + 2 KNO₃

Then coefficients: 1, 2, 1, 2

Type: Ions swap → Double Replacement

Name: Double Replacement

*(Note: If we strictly follow what’s written — “Pb + KI → PbI₂ + KNO₃” — it’s unbalanced and impossible without nitrogen/oxygen source. So we assume intended formula includes nitrate.)*

But wait — looking back at user image description — actually, the third one is:

“_ Pb + _ KI → _ PbI₂ + _ KNO₃”

That’s definitely wrong unless there’s missing info. Perhaps it’s a misprint and should be:

Pb(NO₃)₂ + 2 KI → PbI₂ + 2 KNO₃

I’ll proceed with that assumption since otherwise it’s invalid.

So: Coefficients: 1, 2, 1, 2

Type: Double Replacement

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4. 4 Al + 3 O₂ → 2 Al₂O₃

Check:

Left: Al=4, O=6
Right: Al=4, O=6 → ✔

Type: Two elements form compound → Synthesis

Name: Synthesis

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5. 2 LiF → 2 Li + F₂

Left: Li=2, F=2
Right: Li=2, F=2 → ✔

Type: One compound breaks into elements → Decomposition

Name: Decomposition

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6. 2 H₂O → 2 H₂ + O₂

Left: H=4, O=2
Right: H=4, O=2 → ✔

Type: Water breaks into hydrogen and oxygen → Decomposition

Name: Decomposition

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7. Mg + 2 AgNO₃ → Mg(NO₃)₂ + 2 Ag

Original: _ Mg + _ AgNO₃ → _ Mg(NO₃)₂ + _ Ag

Balance:

Mg: 1 left, 1 right → ok
Ag: need 2 on right → so 2 AgNO₃ on left → then NO₃: 2 on left, 2 on right → good

So: 1 Mg + 2 AgNO₃ → 1 Mg(NO₃)₂ + 2 Ag

Type: Magnesium replaces silver → Single Replacement

Name: Single Replacement

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8. C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O

Glucose combustion.

Left: C=6, H=12, O=6+12=18
Right: C=6, H=12, O=12+6=18 → ✔

Type: Organic compound + oxygen → CO₂ + H₂O → Combustion

Name: Combustion

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9. 2 KClO₃ → 2 KCl + 3 O₂

Original: _ KClO₃ → _ KCl + _ O₂

Balance:

K: 1→1, Cl:1→1, O:3→2 → need even O on right.

Try 2 KClO₃ → 2 KCl + 3 O₂

Left: K=2, Cl=2, O=6
Right: K=2, Cl=2, O=6 → ✔

Type: Compound breaks down → Decomposition

Name: Decomposition

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10. 2 Al + 3 CuSO₄ → Al₂(SO₄)₃ + 3 Cu

Original: _ Al + _ CuSO₄ → _ Al₂(SO₄)₃ + _ Cu

Al: need 2 on left → 2 Al
Cu: 3 on right → so 3 CuSO₄ on left
SO₄: 3 on left, 3 on right → good

So: 2 Al + 3 CuSO₄ → 1 Al₂(SO₄)₃ + 3 Cu

Type: Aluminum replaces copper → Single Replacement

Name: Single Replacement

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Now, compiling all answers:

──────────────────────────────────────

Final Answer:

1. Cl₂ + 2 NaBr → Br₂ + 2 NaCl
Name: Single Replacement

2. 2 Al + Fe₂O₃ → Al₂O₃ + 2 Fe
Name: Single Replacement

3. Pb(NO₃)₂ + 2 KI → PbI₂ + 2 KNO₃ *(assuming corrected formula)*
Name: Double Replacement
*(Note: Original "Pb + KI" is chemically inconsistent; assumed Pb(NO₃)₂ was intended)*

4. 4 Al + 3 O₂ → 2 Al₂O₃
Name: Synthesis

5. 2 LiF → 2 Li + F₂
Name: Decomposition

6. 2 H₂O → 2 H₂ + O₂
Name: Decomposition

7. Mg + 2 AgNO₃ → Mg(NO₃)₂ + 2 Ag
Name: Single Replacement

8. C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O
Name: Combustion

9. 2 KClO₃ → 2 KCl + 3 O₂
Name: Decomposition

10. 2 Al + 3 CuSO₄ → Al₂(SO₄)₃ + 3 Cu
Name: Single Replacement

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✔ All equations are now balanced and classified correctly based on standard reaction types.

If you’re unsure about #3, double-check with your teacher — the original may have a typo. But in most textbooks, that reaction uses lead(II) nitrate, not elemental lead.