Balancing Equations Worksheets And Answers - Free Printable

Let's go through the Balancing Chemical Equations worksheet and verify or correct each equation. The goal is to ensure that the number of atoms for each element is equal on both sides (reactants and products), following the Law of Conservation of Mass.

We'll examine each equation one by one, check if it’s balanced, and explain any corrections needed.

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1) N₂ + H₂ → NH₃

Given:
N₂ + 3H₂ → 2NH₃

✔ Correct!
- Left: 2 N, 6 H
- Right: 2 N (in 2NH₃), 6 H
✔️ Balanced

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2) KClO₃ → KCl + O₂

Given:
2KClO₃ → 2KCl + 3O₂

✔ Correct!
- Left: 2 K, 2 Cl, 6 O
- Right: 2 K, 2 Cl, 6 O (from 3O₂)
✔️ Balanced

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3) NaCl + F₂ → NaF + Cl₂

Given:
2NaCl + F₂ → 2NaF + Cl₂

✔ Correct!
- Left: 2 Na, 2 Cl, 2 F
- Right: 2 Na, 2 F, 2 Cl
✔️ Balanced

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4) H₂ + O₂ → H₂O

Given:
2H₂ + O₂ → 2H₂O

✔ Correct!
- Left: 4 H, 2 O
- Right: 4 H, 2 O
✔️ Balanced

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5) Pb(OH)₂ + HCl → H₂O + PbCl₂

Given:
Pb(OH)₂ + 2HCl → 2H₂O + PbCl₂

✔ Correct!
- Left: Pb, 2 O, 2 H (from OH), 2 H (from HCl), 2 Cl → total: Pb, 4 H, 2 O, 2 Cl
- Right: 2 H₂O → 4 H, 2 O; PbCl₂ → Pb, 2 Cl
✔️ Balanced

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6) AlBr₃ + K₂SO₄ → KBr + Al₂(SO₄)₃

Given:
2AlBr₃ + 3K₂SO₄ → 6KBr + Al₂(SO₄)₃

✔ Correct!
- Left: 2 Al, 6 Br, 6 K, 3 SO₄ → 3 S, 12 O
- Right: 6 KBr → 6 K, 6 Br; Al₂(SO₄)₃ → 2 Al, 3 S, 12 O
✔️ Balanced

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7) CH₄ + O₂ → CO₂ + H₂O

Given:
CH₄ + 2O₂ → CO₂ + 2H₂O

✔ Correct!
- Left: C, 4 H, 4 O
- Right: C, 2 O (CO₂), 2 H₂O → 4 H, 2 O → total 4 O
✔️ Balanced

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8) C₂H₆ + O₂ → CO₂ + H₂O

Given:
C₂H₆ + 5/2 O₂ → 2CO₂ + 3H₂O — but written as:
C₂H₆ + 5O₂ → 3CO₂ + 4H₂O ✘

Wait — the student wrote:
C₂H₆ + 5O₂ → 3CO₂ + 4H₂O → Let's check:

- Left: C₂H₆ → 2 C, 6 H; 5O₂ → 10 O
- Right: 3CO₂ → 3 C, 6 O; 4H₂O → 8 H, 4 O → total: 3 C, 8 H, 10 O

✘ Not balanced: Carbon (2 vs 3), Hydrogen (6 vs 8)

Correct balance:
2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O

But since the student has a star next to this, maybe they made an error.

Wait — the answer shown is:
C₂H₆ + 5O₂ → 3CO₂ + 4H₂O — which is wrong.

✔ Correct should be:
C₂H₆ + 7/2 O₂ → 2CO₂ + 3H₂O, or multiply by 2:
2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O

So, student’s answer is incorrect.

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9) C₄H₁₈ + O₂ → CO₂ + H₂O

Wait — C₄H₁₈? That’s not a real hydrocarbon. Typical is C₄H₁₀ (butane). But let’s assume it's a typo and it's C₄H₁₀?

But the student wrote:
2C₄H₁₈ + 25O₂ → 16CO₂ + 18H₂O

But C₄H₁₈ doesn’t exist. It should be C₄H₁₀.

But assuming the formula is correct as written (maybe it's a hypothetical), let’s test:

Left:
2 C₄H₁₈ → 8 C, 36 H
25 O₂ → 50 O

Right:
16 CO₂ → 16 C, 32 O
18 H₂O → 36 H, 18 O → total O: 50

But carbon: 8 left, 16 right → ✘

So clearly, incorrect.

If it were C₄H₁₀, then:

2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O

But here, student wrote:
2C₄H₁₈ + 25O₂ → 16CO₂ + 18H₂O

→ 2×4 = 8 C on left, 16 on right → ✘

So this is wrong.

But perhaps it was meant to be C₈H₁₈ (octane)? Let's try:

C₈H₁₈ + O₂ → CO₂ + H₂O

Balanced:
2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O

Yes! That matches what’s written.

So likely, the reactant was C₈H₁₈, not C₄H₁₈.

So the equation is:
2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O

✔ Correct if it's C₈H₁₈

So probably a typo in the problem or in the student’s writing.

Assuming C₈H₁₈, then ✔ Correct.

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10) FeCl₃ + NaOH → Fe(OH)₃ + NaCl

Given:
FeCl₃ + 3NaOH → Fe(OH)₃ + 3NaCl

✔ Correct!
- Left: Fe, 3 Cl, 3 Na, 3 O, 3 H
- Right: Fe(OH)₃ → Fe, 3 O, 3 H; 3NaCl → 3 Na, 3 Cl
✔️ Balanced

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11) P + O₂ → P₂O₅

Given:
4P + 5O₂ → 2P₂O₅

✔ Correct!
- Left: 4 P, 10 O
- Right: 2P₂O₅ → 4 P, 10 O
✔️ Balanced

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12) Na + H₂O → NaOH + H₂

Given:
2Na + 2H₂O → 2NaOH + H₂

✔ Correct!
- Left: 2 Na, 4 H, 2 O
- Right: 2 NaOH → 2 Na, 2 O, 2 H; H₂ → 2 H → total 4 H, 2 O, 2 Na
✔️ Balanced

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13) Ag₂O → Ag + O₂

Given:
2Ag₂O → 4Ag + O₂

✔ Correct!
- Left: 4 Ag, 2 O
- Right: 4 Ag, 2 O (in O₂)
✔️ Balanced

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14) S₈ + O₂ → SO₃

Given:
S₈ + 12O₂ → 8SO₃

✔ Correct!
- Left: 8 S, 24 O
- Right: 8 SO₃ → 8 S, 24 O
✔️ Balanced

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15) CO₂ + H₂O → C₆H₁₂O₆ + O₂

This is photosynthesis.

Given:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

✔ Correct!
- Left: 6 C, 12 O, 12 H, 6 O → total 18 O, 12 H, 6 C
- Right: C₆H₁₂O₆ → 6 C, 12 H, 6 O; 6O₂ → 12 O → total 18 O
✔️ Balanced

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16) K + MgBr₂ → KBr + Mg

Given:
2K + MgBr₂ → 2KBr + Mg

✔ Correct!
- Left: 2 K, Mg, 2 Br
- Right: 2 KBr → 2 K, 2 Br; Mg
✔️ Balanced

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17) HCl + CaCO₃ → CaCl₂ + H₂O + CO₂

Given:
2HCl + CaCO₃ → CaCl₂ + H₂O + CO₂

✔ Correct!
- Left: 2 H, 2 Cl, Ca, C, 3 O
- Right: CaCl₂ → Ca, 2 Cl; H₂O → 2 H, 1 O; CO₂ → C, 2 O → total: 2 H, 2 Cl, Ca, C, 3 O
✔️ Balanced

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18) HNO₃ + NaHCO₃ → NaNO₃ + H₂O + CO₂

Given:
HNO₃ + NaHCO₃ → NaNO₃ + H₂O + CO₂

✔ Correct!
All atoms match:
- H: 1+1=2 → H₂O → 2 H
- N: 1 → 1
- O: 3 + 3 = 6 → 3 (NaNO₃) + 1 (H₂O) + 2 (CO₂) = 6
- Na: 1 → 1
- C: 1 → 1
✔️ Balanced

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19) H₂O + O₂ → H₂O₂

Given:
2H₂O + O₂ → 2H₂O₂

Wait — this is not correct.

H₂O₂ is hydrogen peroxide.
But:
Left: 2H₂O → 4 H, 2 O; O₂ → 2 O → total: 4 H, 4 O
Right: 2H₂O₂ → 4 H, 4 O

So 2H₂O + O₂ → 2H₂O₂ is actually balanced!

But is this reaction realistic? Not typically, but mathematically, yes.

✔ So correct as written.

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20) NaBr + CaF₂ → NaF + CaBr₂

Given:
2NaBr + CaF₂ → 2NaF + CaBr₂

✔ Correct!
- Left: 2 Na, 2 Br, Ca, 2 F
- Right: 2 NaF → 2 Na, 2 F; CaBr₂ → Ca, 2 Br
✔️ Balanced

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21) H₂SO₄ + NaNO₂ → HNO₂ + Na₂SO₄

Given:
H₂SO₄ + 2NaNO₂ → 2HNO₂ + Na₂SO₄

✔ Correct!
- Left: 2 H, S, 4 O, 2 Na, 2 N, 4 O (from NO₂) → total: 2 H, S, 2 Na, 2 N, 8 O
- Right: 2 HNO₂ → 2 H, 2 N, 4 O; Na₂SO₄ → 2 Na, S, 4 O → total: 2 H, 2 Na, S, 2 N, 8 O
✔️ Balanced

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## ✔ Summary of Corrections:

| Problem | Student Answer | Correct? | Notes |
|--------|----------------|----------|-------|
| 1 | N₂ + 3H₂ → 2NH₃ | ✔ | Correct |
| 2 | 2KClO₃ → 2KCl + 3O₂ | ✔ | Correct |
| 3 | 2NaCl + F₂ → 2NaF + Cl₂ | ✔ | Correct |
| 4 | 2H₂ + O₂ → 2H₂O | ✔ | Correct |
| 5 | Pb(OH)₂ + 2HCl → 2H₂O + PbCl₂ | ✔ | Correct |
| 6 | 2AlBr₃ + 3K₂SO₄ → 6KBr + Al₂(SO₄)₃ | ✔ | Correct |
| 7 | CH₄ + 2O₂ → CO₂ + 2H₂O | ✔ | Correct |
| 8 | C₂H₆ + 5O₂ → 3CO₂ + 4H₂O | ✘ | Incorrect – should be C₂H₆ + 7/2O₂ → 2CO₂ + 3H₂O |
| 9 | 2C₄H₁₈ + 25O₂ → 16CO₂ + 18H₂O | ✘ | Formula wrong – likely C₈H₁₈ instead of C₄H₁₈ |
| 10 | FeCl₃ + 3NaOH → Fe(OH)₃ + 3NaCl | ✔ | Correct |
| 11 | 4P + 5O₂ → 2P₂O₅ | ✔ | Correct |
| 12 | 2Na + 2H₂O → 2NaOH + H₂ | ✔ | Correct |
| 13 | 2Ag₂O → 4Ag + O₂ | ✔ | Correct |
| 14 | S₈ + 12O₂ → 8SO₃ | ✔ | Correct |
| 15 | 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ | ✔ | Correct |
| 16 | 2K + MgBr₂ → 2KBr + Mg | ✔ | Correct |
| 17 | 2HCl + CaCO₃ → CaCl₂ + H₂O + CO₂ | ✔ | Correct |
| 18 | HNO₃ + NaHCO₃ → NaNO₃ + H₂O + CO₂ | ✔ | Correct |
| 19 | 2H₂O + O₂ → 2H₂O₂ | ✔ | Balanced, though not common |
| 20 | 2NaBr + CaF₂ → 2NaF + CaBr₂ | ✔ | Correct |
| 21 | H₂SO₄ + 2NaNO₂ → 2HNO₂ + Na₂SO₄ | ✔ | Correct |

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🔧 Final Corrections Needed:

#### Problem 8:
Incorrect: C₂H₆ + 5O₂ → 3CO₂ + 4H₂O
Correct:
C₂H₆ + 7/2 O₂ → 2CO₂ + 3H₂O
or better:
2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O

#### Problem 9:
Incorrect: 2C₄H₁₈ + 25O₂ → 16CO₂ + 18H₂O
Likely intended: 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O
(Octane combustion)

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✔ Final Answer:

Most equations are correctly balanced except:

- #8: Should be 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O
- #9: Likely 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O (assuming typo in formula)

All others are correctly balanced.

Let me know if you'd like the corrected version printed out!