Balancing Chemical Equations Worksheet featuring 25 practice problems with chemical formulas and reaction equations.

Let’s go through each equation one by one and balance them step by step. Balancing means making sure the number of atoms of each element is the same on both sides of the arrow.

We’ll check each one carefully.

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1. H₂ + O₂ → H₂O

Left: 2 H, 2 O
Right: 2 H, 1 O → Need more O on right → put 2 in front of H₂O → now 4 H, 2 O on right → so need 2 H₂ on left

→ 2 H₂ + O₂ → 2 H₂O ✔ (already correct as written)

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2. N₂ + H₂ → NH₃

Left: 2 N, 2 H
Right: 1 N, 3 H → To balance N: put 2 in front of NH₃ → now 2 N, 6 H on right → so need 3 H₂ on left (since 3×2=6 H)

→ N₂ + 3 H₂ → 2 NH₃ ✔

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3. S₈ + O₂ → SO₃

Left: 8 S, 2 O
Right: 1 S, 3 O → Put 8 in front of SO₃ → now 8 S, 24 O on right → so need 12 O₂ on left (12×2=24 O)

→ S₈ + 12 O₂ → 8 SO₃ ✔

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4. N₂ + H₂ → N₂O

Left: 2 N, 2 H
Right: 2 N, 1 O → No H on right? Wait — product is N₂O? That has no H. But reactant has H₂. That can’t be right unless it's a typo? Actually, looking at original: it says “N₂ + _ H₂ → _ N₂O” — but that doesn’t make sense because hydrogen disappears. Maybe it’s supposed to be something else? Wait — perhaps it’s N₂ + H₂ → NH₃? But no, problem says N₂O.

Wait — let me double-check the original image text: “4. __ N₂ + __ H₂ → __ N₂O”

That must be a mistake — you can’t have H₂ turning into nothing. Unless… maybe it’s a different reaction? Or perhaps it’s N₂ + O₂ → N₂O? But it says H₂.

Actually, looking again — maybe it’s a trick? Or misprint? But in many worksheets, this might be intended as:

Perhaps it’s meant to be: N₂ + H₂ → NH₃? But that’s #2.

Wait — let’s look at the answer given in the worksheet: it shows “__ N₂ + __ H₂ → __ N₂O” with blanks filled as 2, ?, ? — actually in the user’s image, for #4 it’s written as:

“4. __ N₂ + __ H₂ → __ N₂O” and below it has “2” under N₂, blank under H₂, blank under N₂O? Wait no — in the user’s input, it’s listed as:

Looking back at user’s message:

> 4. __ N₂ + __ H₂ → __ N₂O

But then in the list, after #3, it says:

> 4. __ N₂ + __ H₂ → __ N₂O

And then #5 is Mg + O₂ → MgO

Wait — I think there might be a formatting issue. Let me re-read the user’s input carefully.

User wrote:

```
1. 2 H₂ + 1 O₂ → 2 H₂O
2. 1 N₂ + 3 H₂ → 2 NH₃
3. 1 S₈ + 12 O₂ → 8 SO₃
4. 2 N₂ + ? H₂ → ? N₂O ← wait, no — in user’s text it’s:
```

Actually, in the user’s original message, for #4 it’s:

> 4. __ N₂ + __ H₂ → __ N₂O

But then in the sequence, it’s followed by:

> 5. 2 Mg + 1 O₂ → 2 MgO

So perhaps #4 is incorrectly transcribed? Because chemically, N₂ + H₂ → N₂O doesn't balance — hydrogen atoms vanish.

Wait — maybe it’s a typo and should be N₂ + O₂ → N₂O? Let’s assume that for now, since otherwise it’s impossible.

If it’s N₂ + O₂ → N₂O:

Left: 2 N, 2 O
Right: 2 N, 1 O → so put 2 in front of N₂O → 4 N, 2 O on right → so need 2 N₂ on left → 2 N₂ + O₂ → 2 N₂O

But the reactant has H₂, not O₂. This is confusing.

Alternatively, perhaps it’s N₂H₄ or something? But the formula is written as N₂O.

Wait — looking at the user’s input again:

In the very first line of the worksheet description, it says:

"Balancing Chemical Equations Worksheet"

Then lists:

1. 2 H₂ + 1 O₂ → 2 H₂O
2. 1 N₂ + 3 H₂ → 2 NH₃
3. 1 S₈ + 12 O₂ → 8 SO₃
4. 2 N₂ + __ H₂ → __ N₂O ← here it has "2" already filled for N₂? In user’s text it’s "__ N₂", but in some versions, coefficients are pre-filled.

Actually, in the user’s message, for #4 it’s written as:

> 4. __ N₂ + __ H₂ → __ N₂O

But then in the list, after #3, it’s #4, and then #5 is Mg + O₂ → MgO with 2,1,2 filled.

I think there might be a mistake in the problem itself. However, in many standard worksheets, #4 is often:

N₂ + H₂ → NH₃ — but that’s #2.

Another possibility: perhaps it’s N₂ + O₂ → NO or something.

Wait — let’s skip and come back. Maybe it’s a typo and should be N₂ + O₂ → N₂O, and the H₂ is a mistake.

Assume that for balancing purposes, we ignore H₂ or it’s a error. But that’s not good.

Alternatively, perhaps it’s 2N₂ + H₂ → 2N₂H? No.

I recall that sometimes N₂O is formed from ammonium nitrate, but not from N₂ and H₂.

Perhaps the intended equation is: 2N₂ + O₂ → 2N₂O

And the H₂ is a typo. Since in the user’s input, for #4, it’s listed as "__ N₂ + __ H₂ → __ N₂O", but in many online sources, a common problem is:

N₂ + O₂ → N₂O which balances as 2N₂ + O₂ → 2N₂O

So I’ll assume that "H₂" is a typo and should be "O₂". Otherwise, it’s unbalanceable.

So for #4: 2 N₂ + 1 O₂ → 2 N₂O

But the problem says H₂. Hmm.

Wait — let’s look at the next ones.

#5: Mg + O₂ → MgO → balanced as 2Mg + O₂ → 2MgO ✔

#6: HgO → Hg + O₂ → 2HgO → 2Hg + O₂ ✔

#7: CO₂ + H₂O → C₆H₁₂O₆ + O₂ → photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ ✔

#8: Zn + HCl → ZnCl₂ + H₂ → Zn + 2HCl → ZnCl₂ + H₂ ✔

#9: SiCl₄ + H₂O → H₄SiO₄ + HCl → SiCl₄ + 4H₂O → H₄SiO₄ + 4HCl ✔

#10: Na + H₂O → NaOH + H₂ → 2Na + 2H₂O → 2NaOH + H₂ ✔

#11: C₈H₁₈ + O₂ → CO₂ + H₂O → combustion: 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O ✔

#12: CO₂ + NH₃ → OC(NH₂)₂ + H₂O → urea synthesis: CO₂ + 2NH₃ → OC(NH₂)₂ + H₂O ✔

#13: SiH₄ + O₂ → SiO₂ + H₂O → SiH₄ + 2O₂ → SiO₂ + 2H₂O ✔

#14: Al(OH)₃ + H₂SO₄ → Al₂(SO₄)₃ + H₂O → 2Al(OH)₃ + 3H₂SO₄ → Al₂(SO₄) + 6H₂O ✔

#15: Fe + O₂ → Fe₂O₃ → 4Fe + 3O₂ → 2Fe₂O₃ ✔

#16: Fe₂(SO₄)₃ + KOH → K₂SO₄ + Fe(OH)₃ → Fe₂(SO₄) + 6KOH → 3K₂SO₄ + 2Fe(OH)₃ ✔

#17: Ca₃(PO₄)₂ + SiO₂ → P₄O₁₀ + CaSiO₃ → 2Ca₃(PO₄)₂ + 6SiO₂ → P₄O₁₀ + 6CaSiO₃ ✔

#18: H₂SO₄ + HI → H₂S + I₂ + H₂O → H₂SO₄ + 8HI → H₂S + 4I₂ + 4H₂O ✔

#19: FeS₂ + O₂ → Fe₂O₃ + SO₂ → 4FeS₂ + 11O₂ → 2Fe₂O₃ + 8SO₂ ✔

#20: N₂ + H₂ → NH₃ — wait, this is duplicate of #2? In user’s list, #20 is "2 N₂ + 3 H₂ → 2 NH₃" — but that’s not balanced. 2N₂ has 4N, 3H₂ has 6H; 2NH₃ has 2N, 6H — nitrogen not balanced. Should be N₂ + 3H₂ → 2NH₃, so for 2N₂, it should be 2N₂ + 6H₂ → 4NH₃. But in user’s input, it’s written as "2 N₂ + 3 H₂ → 2 NH₃" which is incorrect. Probably a typo in the worksheet or transcription.

In user’s message: "> 20. 2 N₂ + 3 H₂ → 2 NH₃" — this is wrong. Correct is N₂ + 3H₂ → 2NH₃, so if they want 2N₂, it should be 2N₂ + 6H₂ → 4NH₃.

But perhaps it’s a different compound? No.

Maybe it’s N₂ + H₂ → N₂H₄ or something, but it says NH₃.

I think for #20, it’s likely a mistake, and it should be the same as #2.

Similarly, #21: FeO + O₂ → Fe₂O₃ → 4FeO + O₂ → 2Fe₂O₃ ✔

#22: NaOH + H₂SO₄ → Na₂SO₄ + H₂O → 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O ✔

#23: K + Br₂ → KBr → 2K + Br₂ → 2KBr ✔

#24: C₇H₁₆ + O₂ → CO₂ + H₂O → C₇H₁₆ + 11O₂ → 7CO₂ + 8H₂O ✔

#25: P₄ + O₂ → P₂O₅ → P₄ + 5O₂ → 2P₂O₅ ✔

Now back to #4. Given that all others are standard, and #4 has H₂ which doesn't appear in product, I believe it's a typo, and it should be O₂ instead of H₂. So:

4. 2 N₂ + 1 O₂ → 2 N₂O

But to match the format, and since the user has "__ N₂ + __ H₂ → __ N₂O", and in many worksheets, this might be intended as is, but it's impossible. Perhaps it's N₂H₄ decomposition or something.

Another thought: maybe it's 2N₂ + H₂ → 2N₂H, but N₂H is not stable.

I recall that hydrazine is N₂H₄, so perhaps N₂ + 2H₂ → N₂H₄, but product is N₂O.

I think the safest bet is to assume it's a typo and correct to O₂. So for #4: coefficients are 2 for N₂, 1 for O₂, 2 for N₂O.

But since the problem says H₂, and to be faithful, let's see if there's any way.

Suppose the reaction is: 2N₂ + H₂ → 2N₂H, but N₂H isn't standard.

Perhaps it's N₂ + 3H₂ → 2NH₃, but that's #2.

I think for the sake of completing, I'll note that #4 as written is unbalanceable, but in context, it's likely 2N₂ + O₂ → 2N₂O, so coefficients 2,1,2.

Similarly, for #20, "2 N₂ + 3 H₂ → 2 NH₃" is incorrect; it should be 2N₂ + 6H₂ → 4NH₃, or if they mean the same as #2, it's N₂ + 3H₂ → 2NH₃.

In user's input for #20, it's "2 N₂ + 3 H₂ → 2 NH₃", which has 4N left, 2N right — not balanced. So probably a transcription error, and it should be the standard ammonia synthesis.

Perhaps it's a different reaction, like for hydrazine, but unlikely.

I will proceed with the standard balancing for all, and for #4 and #20, use the correct chemical equations.

So final answers:

1. 2,1,2
2. 1,3,2
3. 1,12,8
4. 2,1,2 [assuming O₂ instead of H₂]
5. 2,1,2
6. 2,2,1
7. 6,6,1,6
8. 1,2,1,1
9. 1,4,1,4
10. 2,2,2,1
11. 2,25,16,18
12. 1,2,1,1
13. 1,2,1,2
14. 2,3,1,6
15. 4,3,2
16. 1,6,3,2
17. 2,6,1,6
18. 1,8,1,4,4
19. 4,11,2,8
20. 1,3,2 [correcting to standard ammonia synthesis]
21. 4,1,2
22. 2,1,1,2
23. 2,1,2
24. 1,11,7,8
25. 1,5,2

For #4, if we must keep H₂, it's impossible, so I'll go with the assumption.

Similarly for #20, the given "2 N₂ + 3 H₂ → 2 NH₃" is wrong; correct is 1,3,2 for N₂,H₂,NH₃.

In the user's list, for #20, it's written as "2 N₂ + 3 H₂ → 2 NH₃", which is unbalanced, so likely a mistake, and it should be the same as #2.

So in the final answer, I'll provide the correct coefficients for each.

Final Answer:
1. 2, 1, 2
2. 1, 3, 2
3. 1, 12, 8
4. 2, 1, 2 (assuming O₂ instead of H₂)
5. 2, 1, 2
6. 2, 2, 1
7. 6, 6, 1, 6
8. 1, 2, 1, 1
9. 1, 4, 1, 4
10. 2, 2, 2, 1
11. 2, 25, 16, 18
12. 1, 2, 1, 1
13. 1, 2, 1, 2
14. 2, 3, 1, 6
15. 4, 3, 2
16. 1, 6, 3, 2
17. 2, 6, 1, 6
18. 1, 8, 1, 4, 4
19. 4, 11, 2, 8
20. 1, 3, 2 (corrected from given)
21. 4, 1, 2
22. 2, 1, 1, 2
23. 2, 1, 2
24. 1, 11, 7, 8
25. 1, 5, 2