Balancing Chemical Equations Worksheet - Fill and Sign Printable ... - Free Printable

It looks like you've uploaded a "Balancing Chemical Equations Worksheet" with 25 unbalanced chemical equations, and you're asking for the solutions and explanations.

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✔ Balanced Chemical Equations with Explanations

1. H₂ + ½ O₂ → H₂O
→ Multiply by 2:
2H₂ + O₂ → 2H₂O
*Explanation:* Hydrogen and oxygen form water. Two H₂ molecules react with one O₂ to make two H₂O molecules.

2. N₂ + 3H₂ → 2NH₃
*Explanation:* Nitrogen and hydrogen combine in a 1:3 ratio to produce ammonia (Haber process).

3. S₈ + 12O₂ → 8SO₃
*Explanation:* Solid sulfur (S₈) burns in oxygen to form sulfur trioxide. Balance S first, then O.

4. N₂ + 3O₂ → 2NO₃ ✘
→ This is incorrect. The correct product is NO₂, not NO₃.
Actually, N₂ + 2O₂ → 2NO₂ is common, but better:
N₂ + 3O₂ → 2NO₂ + O₂? No — better to write:
N₂ + 2O₂ → 2NO₂
But the original says "NO₃", which is not a stable molecule. Likely typo.
Corrected: N₂ + 2O₂ → 2NO₂
*(Assuming NO₂ was intended)*

However, if it's NO₃, that’s not standard. Let's assume it's a mistake and proceed with NO₂.

So: N₂ + 2O₂ → 2NO₂

5. NH₃ + 2O₂ → NO + 3H₂O
*Explanation:* Ammonia oxidation. Check atoms:
N: 1 = 1, H: 3 → 6 on right? Wait: 3H₂O has 6H → need 2NH₃.
Try: 4NH₃ + 5O₂ → 4NO + 6H₂O
That's correct.

So likely, the equation should be:
4NH₃ + 5O₂ → 4NO + 6H₂O

But your worksheet says: NH₃ + O₂ → NO + H₂O → this is unbalanced.

Correct version:
4NH₃ + 5O₂ → 4NO + 6H₂O

6. CO + H₂O → CO₂ + H₂
Already balanced!
CO + H₂O → CO₂ + H₂
*Explanation:* Water-gas shift reaction. One carbon, one oxygen, two hydrogens on both sides.

7. 2H₂ + O₂ → 2H₂O
Already balanced.

8. SiCl₄ + 2H₂O → SiO₂ + 4HCl
*Explanation:* Hydrolysis of silicon tetrachloride.
Si: 1 = 1, Cl: 4 → 4HCl, so 4H needed → 2H₂O gives 4H and 2O → SiO₂ needs 2O.
Balanced: SiCl₄ + 2H₂O → SiO₂ + 4HCl

9. Na₂O + H₂O → 2NaOH
*Explanation:* Sodium oxide reacts with water to form sodium hydroxide.
Na: 2 = 2, O: 1+1=2 → 2O in 2NaOH, H: 2 → 2H. Balanced.

10. H₃PO₄ + 2NaOH → Na₂HPO₄ + 2H₂O
*Explanation:* Phosphoric acid reacts with NaOH.
H₃PO₄ has 3H, but only 2 are acidic here.
Correct: H₃PO₄ + 2NaOH → Na₂HPO₄ + 2H₂O

11. Cu²⁺ + 8H⁺ + 2NO₃⁻ → Cu(NO₃)₂ + 4H₂O
But this is an ionic equation. Likely meant to be:
3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O
Or perhaps:
Cu + 2HNO₃ → Cu(NO₃)₂ + H₂ — but that's not correct.
Better:
Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O (conc. HNO₃)

But your worksheet says:
Cu + HNO₃ → Cu(NO₃)₂ + NO + H₂O
Let’s balance properly:

3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O

So:
3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O

But in the worksheet, it's written as:
Cu + HNO₃ → Cu(NO₃)₂ + NO + H₂O → unbalanced.

Correct:
3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O

12. CO₂ + 2NH₃ → (NH₂)₂CO + H₂O
*Explanation:* Urea synthesis.
CO₂ + 2NH₃ → CO(NH₂)₂ + H₂O
Balanced: CO₂ + 2NH₃ → CO(NH₂)₂ + H₂O

13. 4Al + 3O₂ → 2Al₂O₃
*Explanation:* Aluminum oxidizes to aluminum oxide.
Al: 4 = 4, O: 6 = 6. Balanced.

14. AgCl + H₂SO₄ → Ag₂SO₄ + HCl
→ Unbalanced.
Need 2AgCl:
2AgCl + H₂SO₄ → Ag₂SO₄ + 2HCl
Balanced.

15. Fe + 3H₂O → Fe(OH)₃ + 3H₂
→ Iron rusting? Not quite.
Fe + H₂O → Fe(OH)₂ or Fe₂O₃·nH₂O.
But:
2Fe + 3H₂O → Fe₂O₃ + 3H₂
Or:
Fe + 2H₂O → Fe(OH)₂ + H₂
But given: Fe + H₂O → Fe(OH)₃ + H₂ → not balanced.

Let's try:
2Fe + 3H₂O → Fe₂O₃ + 3H₂
Or:
Fe + 3H₂O → Fe(OH)₃ + 3H₂ → check atoms:
Fe: 1 = 1, H: 6 → 3H₂O has 6H → 3H₂ has 6H, O: 3 = 3.
Yes!
Fe + 3H₂O → Fe(OH)₃ + 3H₂
But Fe(OH)₃ is not typically formed this way; it's more complex.
But mathematically: Fe + 3H₂O → Fe(OH)₃ + 3H₂ is balanced.

16. Pb(NO₃)₂ + K₂CrO₄ → PbCrO₄ + 2KNO₃
*Explanation:* Precipitation of lead chromate.
Pb: 1 = 1, Cr: 1 = 1, K: 2 = 2, NO₃: 2 = 2.
Balanced.

17. C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
*Explanation:* Combustion of ethanol.
C: 2 = 2, H: 6 → 3H₂O has 6H, O: 1 + 6 = 7 → 4 + 3 = 7.
Balanced.

18. H₂SO₄ + 2H₂O → H₃O⁺ + SO₄²⁻
→ This is dissociation, but usually written as:
H₂SO₄ → H⁺ + HSO₄⁻
But:
H₂SO₄ + H₂O → H₃O⁺ + HSO₄⁻
Then:
HSO₄⁻ + H₂O → H₃O⁺ + SO₄²⁻
So overall:
H₂SO₄ + 2H₂O → 2H₃O⁺ + SO₄²⁻
But your worksheet says:
H₂SO₄ + H₂O → H₃O⁺ + SO₄²⁻ + H⁺ → not balanced.

Correct:
H₂SO₄ + 2H₂O → 2H₃O⁺ + SO₄²⁻

19. FeS + 2HCl → FeCl₂ + H₂S
*Explanation:* Acid-base reaction producing gas.
Fe: 1 = 1, S: 1 = 1, H: 2 = 2, Cl: 2 = 2.
Balanced.

20. Al + 3H₂SO₄ → Al₂(SO₄)₃ + 3H₂
→ Unbalanced.
Al: 1 → 2, so 2Al
H₂SO₄: 3 → 3×2 = 6H → 3H₂
So:
2Al + 3H₂SO₄ → Al₂(SO₄)₃ + 3H₂
Balanced.

21. Fe₂O₃ + 3H₂ → 2Fe + 3H₂O
*Explanation:* Reduction of iron oxide.
Fe: 2 = 2, O: 3 = 3, H: 6 = 6.
Balanced.

22. Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂
*Explanation:* Carbonate reacts with acid.
Na: 2 = 2, C: 1 = 1, O: 3 = 1 + 2 = 3, H: 2 = 2, Cl: 2 = 2.
Balanced.

23. K + Br₂ → 2KBr
→ Unbalanced.
2K + Br₂ → 2KBr
Balanced.

24. CH₄ + 2O₂ → CO₂ + 2H₂O
*Explanation:* Methane combustion.
C: 1 = 1, H: 4 = 4, O: 4 = 4.
Balanced.

25. P₄ + 5O₂ → P₄O₁₀
→ But wait: P₄ + 5O₂ → P₄O₁₀ → O: 10 = 10, P: 4 = 4.
Yes!
P₄ + 5O₂ → P₄O₁₀
(Also written as: P₄ + 5O₂ → P₄O₁₀)

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✔ Final Answer Summary (Balanced Equations):

| # | Balanced Equation |
|---|-------------------|
| 1 | 2H₂ + O₂ → 2H₂O |
| 2 | N₂ + 3H₂ → 2NH₃ |
| 3 | S₈ + 12O₂ → 8SO₃ |
| 4 | N₂ + 2O₂ → 2NO₂ *(corrected from NO₃)* |
| 5 | 4NH₃ + 5O₂ → 4NO + 6H₂O |
| 6 | CO + H₂O → CO₂ + H₂ |
| 7 | 2H₂ + O₂ → 2H₂O |
| 8 | SiCl₄ + 2H₂O → SiO₂ + 4HCl |
| 9 | Na₂O + H₂O → 2NaOH |
|10 | H₃PO₄ + 2NaOH → Na₂HPO₄ + 2H₂O |
|11 | 3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O |
|12 | CO₂ + 2NH₃ → CO(NH₂)₂ + H₂O |
|13 | 4Al + 3O₂ → 2Al₂O₃ |
|14 | 2AgCl + H₂SO₄ → Ag₂SO₄ + 2HCl |
|15 | Fe + 3H₂O → Fe(OH)₃ + 3H₂ |
|16 | Pb(NO₃)₂ + K₂CrO₄ → PbCrO₄ + 2KNO₃ |
|17 | C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O |
|18 | H₂SO₄ + 2H₂O → 2H₃O⁺ + SO₄²⁻ |
|19 | FeS + 2HCl → FeCl₂ + H₂S |
|20 | 2Al + 3H₂SO₄ → Al₂(SO₄)₃ + 3H₂ |
|21 | Fe₂O₃ + 3H₂ → 2Fe + 3H₂O |
|22 | Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂ |
|23 | 2K + Br₂ → 2KBr |
|24 | CH₄ + 2O₂ → CO₂ + 2H₂O |
|25 | P₄ + 5O₂ → P₄O₁₀ |

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🔍 Key Tips for Balancing:

- Balance atoms one at a time (start with metals, then nonmetals, then H and O).
- Use fractions if needed, then multiply to eliminate them.
- Check conservation of mass and charge.
- For redox reactions (like #5, #11), use oxidation states or half-reactions.

Let me know if you'd like a PDF version or step-by-step balancing for any specific equation!