Balancing Chemical Equations Worksheet for 9th - 12th Grade ... - Free Printable

Let’s go step by step and balance each chemical equation. We’ll make sure the number of atoms for each element is the same on both sides (left = right).

---

1) N₂ + H₂ → NH₃

Left: N=2, H=2
Right: N=1, H=3

Try putting 2 in front of NH₃ → now Right: N=2, H=6
So we need 3 H₂ on left to get 6 H.

→ N₂ + 3H₂ → 2NH₃

✔ Balanced.

---

2) KClO₃ → KCl + O₂

Left: K=1, Cl=1, O=3
Right: K=1, Cl=1, O=2

We need even oxygen on right. Try 2KClO₃ → gives 6 O on left.

Then right needs 3O₂ to give 6 O.

Also, 2KCl on right to match K and Cl.

→ 2KClO₃ → 2KCl + 3O₂

✔ Balanced.

---

3) NaCl + F₂ → NaF + Cl₂

Left: Na=1, Cl=1, F=2
Right: Na=1, F=1, Cl=2

Need 2NaF on right → then Na=2, so 2NaCl on left.

Now Cl=2 on left → matches Cl₂ on right.

F: left has 2 from F₂? Wait — if we have 2NaCl + F₂ → 2NaF + Cl₂

Check:

Left: Na=2, Cl=2, F=2
Right: Na=2, F=2, Cl=2

→ 2NaCl + F₂ → 2NaF + Cl₂

✔ Balanced.

---

4) H₂ + O₂ → H₂O

Left: H=2, O=2
Right: H=2, O=1

Put 2 in front of H₂O → Right: H=4, O=2 → so need 2H₂ on left.

→ 2H₂ + O₂ → 2H₂O

✔ Balanced.

---

5) AgNO₃ + MgCl₂ → AgCl + Mg(NO₃)₂

Left: Ag=1, N=1, O=3, Mg=1, Cl=2
Right: Ag=1, Cl=1, Mg=1, N=2, O=6

Need 2AgCl on right → then Ag=2, so 2AgNO₃ on left.

Now N=2, O=6 on left → matches Mg(NO₃)₂ on right.

Cl: left has 2 from MgCl₂ → right has 2 from 2AgCl.

Mg: 1 on each side.

→ 2AgNO₃ + MgCl₂ → 2AgCl + Mg(NO₃)₂

✔ Balanced.

---

6) AlBr₃ + K₂SO₄ → KBr + Al₂(SO₄)₃

Left: Al=1, Br=3, K=2, S=1, O=4
Right: K=1, Br=1, Al=2, S=3, O=12

Start with Al: need 2AlBr₃ → Al=2, Br=6
Then need 3K₂SO₄ → K=6, S=3, O=12

Right: Al₂(SO₄) → Al=2, S=3, O=12
KBr: need 6KBr → K=6, Br=6

→ 2AlBr₃ + 3K₂SO₄ → 6KBr + Al₂(SO₄)

✔ Balanced.

---

7) CH₄ + O₂ → CO₂ + H₂O

Left: C=1, H=4, O=2
Right: C=1, O=2+1=3? Wait: CO₂ has 2O, H₂O has 1O → total 3O per set.

But H: right has 2H per H₂O → need 2H₂O to get 4H.

So: CH₄ + O₂ → CO₂ + 2H₂O

Now O: right = 2 (from CO₂) + 2 (from 2H₂O) = 4 → so need 2O₂ on left.

→ CH₄ + 2O₂ → CO₂ + 2H₂O

✔ Balanced.

---

8) C₃H₈ + O₂ → CO₂ + H₂O

Left: C=3, H=8, O=2
Right: C=1, H=2, O=3

Need 3CO₂ → C=3
Need 4H₂O → H=8

Now O: right = 3×2 + 4×1 = 6+4=10 → so need 5O₂ on left.

→ C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

✔ Balanced.

---

9) C₈H₁₈ + O₂ → CO₂ + H₂O

Left: C=8, H=18, O=2
Right: C=1, H=2, O=3

Need 8CO₂ → C=8
Need 9H₂O → H=18

O: right = 8×2 + 9×1 = 16+9=25 → so need 25/2 O₂ → multiply all by 2.

→ 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O

✔ Balanced.

---

10) FeCl₃ + NaOH → Fe(OH)₃ + NaCl

Left: Fe=1, Cl=3, Na=1, O=1, H=1
Right: Fe=1, O=3, H=3, Na=1, Cl=1

Need 3NaOH → Na=3, O=3, H=3
Then 3NaCl on right → Cl=3

→ FeCl₃ + 3NaOH → Fe(OH)₃ + 3NaCl

✔ Balanced.

---

11) P₄ + O₂ → P₂O₅

Left: P=4, O=2
Right: P=2, O=5

Need 2P₂O₅ → P=4, O=10 → so need 5O₂ on left.

→ P₄ + 5O₂ → 2P₂O₅

✔ Balanced.

---

12) Na + H₂O → NaOH + H₂

Left: Na=1, H=2, O=1
Right: Na=1, O=1, H=1+2=3? Wait: NaOH has H=1, H₂ has H=2 → total H=3

Not balanced.

Try 2Na + 2H₂O → 2NaOH + H₂

Left: Na=2, H=4, O=2
Right: Na=2, O=2, H=2 (from 2NaOH) + 2 (from H₂) = 4

→ 2Na + 2H₂O → 2NaOH + H₂

✔ Balanced.

---

13) Ag₂O → Ag + O₂

Left: Ag=2, O=1
Right: Ag=1, O=2

Need 2Ag₂O → Ag=4, O=2 → then right: 4Ag + O₂

→ 2Ag₂O → 4Ag + O₂

✔ Balanced.

---

14) S₈ + O₂ → SO₂

Left: S=8, O=2
Right: S=1, O=2

Need 8SO₂ → S=8, O=16 → so need 8O₂ on left.

→ S₈ + 8O₂ → 8SO₂

✔ Balanced.

---

15) CO₂ + H₂O → C₆H₁₂O₆ + O₂

This is photosynthesis.

Left: C=1, O=2+1=3, H=2
Right: C=6, H=12, O=6+2=8? Wait: C₆H₁₂O₆ has O=6, plus O₂ has 2 → but we don’t know how many O₂ yet.

Standard form: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

Check:

Left: C=6, O=12+6=18, H=12
Right: C=6, H=12, O=6 + 12 = 18 (since 6O₂ = 12 O)

→ 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

✔ Balanced.

---

16) K + MgBr₂ → KBr + Mg

Left: K=1, Mg=1, Br=2
Right: K=1, Br=1, Mg=1

Need 2KBr → then K=2, so 2K on left.

→ 2K + MgBr₂ → 2KBr + Mg

✔ Balanced.

---

17) KO + CaSO₄ → CaO + K₂SO₄

Wait — “KO” is not a real compound. Probably typo? Should be K₂O?

Assuming it's K₂O + CaSO₄ → CaO + K₂SO₄

Left: K=2, O=1+4=5? Wait: K₂O has O=1, CaSO₄ has O=4 → total O=5
Ca=1, S=1

Right: CaO → Ca=1, O=1; K₂SO₄ → K=2, S=1, O=4 → total O=5

Already balanced!

→ K₂O + CaSO₄ → CaO + K₂SO₄

✔ Balanced. *(assuming KO was meant to be K₂O)*

If it really says "KO", that’s invalid — but since this is homework, likely typo. We’ll go with K₂O.

---

18) HNO₃ + NaHCO₃ → NaNO₃ + H₂O + CO₂

Left: H=1+1=2, N=1, O=3+3=6, Na=1, C=1
Right: Na=1, N=1, O=3+1+2=6, H=2, C=1

Already balanced!

→ HNO₃ + NaHCO₃ → NaNO₃ + H₂O + CO₂

✔ Balanced.

---

19) PbO + C → Pb + CO₂

Left: Pb=1, O=1, C=1
Right: Pb=1, C=1, O=2

Need 2PbO → Pb=2, O=2 → then need 2Pb on right.

C: need 1C → makes 1CO₂ → O=2 → good.

But Pb: left=2, right=2 → ok.

Wait: 2PbO + C → 2Pb + CO₂

Check O: left=2, right=2 → yes.

C: 1=1

Pb: 2=2

→ 2PbO + C → 2Pb + CO₂

✔ Balanced.

---

20) NaBr + CaF₂ → NaF + CaBr₂

Left: Na=1, Br=1, Ca=1, F=2
Right: Na=1, F=1, Ca=1, Br=2

Need 2NaBr → Na=2, Br=2
Then 2NaF → Na=2, F=2
CaF₂ already has Ca=1, F=2 → matches.

CaBr₂ → Ca=1, Br=2 → matches.

→ 2NaBr + CaF₂ → 2NaF + CaBr₂

✔ Balanced.

---

Final Answer:

1) N₂ + 3H₂ → 2NH₃
2) 2KClO₃ → 2KCl + 3O₂
3) 2NaCl + F₂ → 2NaF + Cl₂
4) 2H₂ + O₂ → 2H₂O
5) 2AgNO₃ + MgCl₂ → 2AgCl + Mg(NO₃)₂
6) 2AlBr₃ + 3K₂SO₄ → 6KBr + Al₂(SO₄)₃
7) CH₄ + 2O₂ → CO₂ + 2H₂O
8) C₃H₈ + 5O₂ → 3CO₂ + 4H₂O
9) 2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O
10) FeCl₃ + 3NaOH → Fe(OH)₃ + 3NaCl
11) P₄ + 5O₂ → 2P₂O₅
12) 2Na + 2H₂O → 2NaOH + H₂
13) 2Ag₂O → 4Ag + O₂
14) S₈ + 8O₂ → 8SO₂
15) 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
16) 2K + MgBr₂ → 2KBr + Mg
17) K₂O + CaSO₄ → CaO + K₂SO₄ *(assuming KO was typo for K₂O)*
18) HNO₃ + NaHCO₃ → NaNO₃ + H₂O + CO₂
19) 2PbO + C → 2Pb + CO₂
20) 2NaBr + CaF₂ → 2NaF + CaBr₂