Grade 9 Physical Science: Chemical Reactions] Balancing equations ... - Free Printable

Let’s go through each equation one by one and balance them. We’ll make sure the number of atoms of each element is the same on both sides.

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1. Na₃PO₄ + KOH → NaOH + K₃PO₄

Left: Na=3, P=1, O=4+1=5, K=1, H=1
Right: Na=1, O=1+4=5, H=1, K=3, P=1

We need 3 Na on right → put 3 in front of NaOH
Now right has 3 Na, 3 O from NaOH + 4 from K₃PO₄ = 7 O? Wait — let’s recount carefully.

Actually, better to balance polyatomic ions if they stay together.

PO₄ stays as PO₄ → so we can treat it as a unit.

Na₃PO₄ has 3 Na → need 3 NaOH on right → so coefficient 3 for NaOH
Then K₃PO₄ needs 3 K → so 3 KOH on left

Check:

Left: Na₃PO₄ + 3KOH → 3NaOH + K₃PO₄
Na: 3 = 3
P: 1 = 1
O: 4 + 3 = 7; right: 3 (from 3NaOH) + 4 (from K₃PO₄) = 7
K: 3 = 3
H: 3 = 3

✔ Balanced: 1, 3, 3, 1

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2. MgF₂ + Li₂CO₃ → MgCO₃ + LiF

Left: Mg=1, F=2, Li=2, C=1, O=3
Right: Mg=1, C=1, O=3, Li=1, F=1

Need 2 LiF on right to match Li and F

→ MgF₂ + Li₂CO₃ → MgCO₃ + 2LiF

Check:
Mg:1=1, F:2=2, Li:2=2, C:1=1, O:3=3 ✔

Coefficients: 1, 1, 1, 2

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3. P₄ + O₂ → P₂O₃

Left: P=4, O=2
Right: P=2, O=3

Need even P on right → try 2 P₂O₃ → P=4, O=6

So O₂ must be 3 → because 3×2=6

→ P₄ + 3O₂ → 2P₂O₃

Check: P:4=4, O:6=6 ✔

Coefficients: 1, 3, 2

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4. RbNO₃ + BeF₂ → Be(NO₃)₂ + RbF

Left: Rb=1, N=1, O=3, Be=1, F=2
Right: Be=1, N=2, O=6, Rb=1, F=1

Need 2 RbNO₃ on left → gives 2Rb, 2N, 6O
Then right needs 2 RbF → to match Rb and F

BeF₂ already has 2F → good

→ 2RbNO₃ + BeF₂ → Be(NO₃)₂ + 2RbF

Check:
Rb:2=2, N:2=2, O:6=6, Be:1=1, F:2=2 ✔

Coefficients: 2, 1, 1, 2

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5. AgNO₃ + Cu → Cu(NO₃)₂ + Ag

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

Need 2 AgNO₃ on left → 2Ag, 2N, 6O
Then right needs 2 Ag

→ 2AgNO₃ + Cu → Cu(NO₃)₂ + 2Ag

Check: Ag:2=2, N:2=2, O:6=6, Cu:1=1 ✔

Coefficients: 2, 1, 1, 2

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6. CF₄ + Br₂ → CBr₄ + F₂

Left: C=1, F=4, Br=2
Right: C=1, Br=4, F=2

Need 2 Br₂ on left → 4 Br
Need 2 F₂ on right → 4 F

→ CF₄ + 2Br₂ → CBr₄ + 2F₂

Check: C:1=1, F:4=4, Br:4=4 ✔

Coefficients: 1, 2, 1, 2

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7. HCN + CuSO₄ → H₂SO₄ + Cu(CN)₂

Left: H=1, C=1, N=1, Cu=1, S=1, O=4
Right: H=2, S=1, O=4, Cu=1, C=2, N=2

Need 2 HCN on left → 2H, 2C, 2N
Then right: Cu(CN)₂ already has 2C, 2N → good
But H₂SO₄ needs 2H → matches

→ 2HCN + CuSO₄ → H₂SO₄ + Cu(CN)₂

Check: H:2=2, C:2=2, N:2=2, Cu:1=1, S:1=1, O:4=4 ✔

Coefficients: 2, 1, 1, 1

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8. GaF₃ + Cs → CsF + Ga

Left: Ga=1, F=3, Cs=1
Right: Cs=1, F=1, Ga=1

Need 3 CsF on right → 3Cs, 3F
So need 3 Cs on left

→ GaF₃ + 3Cs → 3CsF + Ga

Check: Ga:1=1, F:3=3, Cs:3=3 ✔

Coefficients: 1, 3, 3, 1

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9. BaS + PtF₂ → BaF₂ + PtS

Left: Ba=1, S=1, Pt=1, F=2
Right: Ba=1, F=2, Pt=1, S=1

Already balanced!

Coefficients: 1, 1, 1, 1

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10. N₂ + H₂ → NH₃

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

Need 2 NH₃ → N=2, H=6
So H₂ must be 3 → 6H

→ N₂ + 3H₂ → 2NH₃

Check: N:2=2, H:6=6 ✔

Coefficients: 1, 3, 2

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11. NaF + Br₂ → NaBr + F₂

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

Need 2 NaF → 2Na, 2F
Need 2 NaBr → 2Na, 2Br
Br₂ already gives 2Br → good
F₂ gives 2F → good

→ 2NaF + Br₂ → 2NaBr + F₂

Check: Na:2=2, F:2=2, Br:2=2 ✔

Coefficients: 2, 1, 2, 1

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12. Pb(OH)₂ + HCl → H₂O + PbCl₂

Left: Pb=1, O=2, H=2+1=3, Cl=1
Wait — Pb(OH)₂ has 2O and 2H, plus HCl has 1H and 1Cl → total H=3? That’s messy.

Better: Pb(OH)₂ has Pb, 2O, 2H
HCl has H, Cl

Right: H₂O has 2H, 1O; PbCl₂ has Pb, 2Cl

So need 2 HCl to get 2Cl → then H from HCl: 2H, plus 2H from Pb(OH)₂ → total 4H → need 2 H₂O (which uses 4H and 2O)

→ Pb(OH)₂ + 2HCl → 2H₂O + PbCl₂

Check: Pb:1=1, O:2=2, H:2+2=4 = 4 (in 2H₂O), Cl:2=2 ✔

Coefficients: 1, 2, 2, 1

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13. 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

Need 2 AlBr₃ → 2Al, 6Br
Need 3 K₂SO₄ → 6K, 3S, 12O
Right: Al₂(SO₄)₃ → 2Al, 3S, 12O → good
KBr: need 6K and 6Br → so 6KBr

→ 2AlBr₃ + 3K₂SO₄ → 6KBr + Al₂(SO₄)₃

Check: Al:2=2, Br:6=6, K:6=6, S:3=3, O:12=12 ✔

Coefficients: 2, 3, 6, 1

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14. 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? But H=2 per H₂O

Need 2 H₂O → 4H, 2O
CO₂ → 1C, 2O
Total O on right: 2+2=4 → so O₂ must be 2 → 4O

→ CH₄ + 2O₂ → CO₂ + 2H₂O

Check: C:1=1, H:4=4, O:4=4 ✔

Coefficients: 1, 2, 1, 2

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15. Na₃PO₄ + CaCl₂ → NaCl + Ca₃(PO)₂

Left: Na=3, P=1, O=4, Ca=1, Cl=2
Right: Na=1, Cl=1, Ca=3, P=2, O=8

Need 2 Na₃PO₄ → 6Na, 2P, 8O
Need 3 CaCl₂ → 3Ca, 6Cl
Right: Ca₃(PO₄)₂ → 3Ca, 2P, 8O → good
NaCl: need 6Na and 6Cl → so 6NaCl

→ 2Na₃PO₄ + 3CaCl₂ → 6NaCl + Ca₃(PO₄)₂

Check: Na:6=6, P:2=2, O:8=8, Ca:3=3, Cl:6=6 ✔

Coefficients: 2, 3, 6, 1

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16. K + Cl₂ → KCl

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

Need 2 KCl → 2K, 2Cl
So 2 K on left

→ 2K + Cl₂ → 2KCl

Check: K:2=2, Cl:2=2 ✔

Coefficients: 2, 1, 2

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17. Al + HCl → H₂ + AlCl₃

Left: Al=1, H=1, Cl=1
Right: H=2, Al=1, Cl=3

Need 2 AlCl₃? No — better:

AlCl₃ has 3Cl → so need 3 HCl → 3H, 3Cl
But H₂ needs even H → so 6 HCl → 6H, 6Cl
Then 2 AlCl₃ → 2Al, 6Cl
And 3 H₂ → 6H

Also need 2 Al on left

→ 2Al + 6HCl → 3H₂ + 2AlCl₃

Check: Al:2=2, H:6=6, Cl:6=6 ✔

Coefficients: 2, 6, 3, 2

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18. N₂ + F₂ → NF₃

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

Need 2 NF₃ → 2N, 6F
So F₂ must be 3 → 6F

→ N₂ + 3F₂ → 2NF₃

Check: N:2=2, F:6=6 ✔

Coefficients: 1, 3, 2

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19. SO₂ + Li₂Se → SSe₂ + Li₂O

Left: S=1, O=2, Li=2, Se=1
Right: S=1, Se=2, Li=2, O=1

Need 2 Li₂O → 4Li, 2O → but left only has 2Li → not matching

Wait — right: SSe₂ has 1S, 2Se
Li₂O has 2Li, 1O

Left: SO₂ has 1S, 2O; Li₂Se has 2Li, 1Se

To get 2Se on right, need 2 Li₂Se → 4Li, 2Se
Then right: SSe₂ → still 1S, 2Se → good
Li₂O: need 4Li → so 2 Li₂O → 4Li, 2O → matches SO₂'s 2O

S: left 1, right 1 → good

→ SO₂ + 2Li₂Se → SSe₂ + 2Li₂O

Check: S:1=1, O:2=2, Li:4=4, Se:2=2 ✔

Coefficients: 1, 2, 1, 2

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20. NH₃ + H₂SO₄ → (NH₄)₂SO₄

Left: N=1, H=3+2=5, S=1, O=4
Right: N=2, H=8, S=1, O=4

Need 2 NH₃ → 2N, 6H
Plus H₂SO₄ → 2H, so total H=8 → perfect

→ 2NH₃ + H₂SO₄ → (NH₄)₂SO₄

Check: N:2=2, H:6+2=8=8, S:1=1, O:4=4 ✔

Coefficients: 2, 1, 1

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Final Answer:
1. 1, 3, 3, 1
2. 1, 1, 1, 2
3. 1, 3, 2
4. 2, 1, 1, 2
5. 2, 1, 1, 2
6. 1, 2, 1, 2
7. 2, 1, 1, 1
8. 1, 3, 3, 1
9. 1, 1, 1, 1
10. 1, 3, 2
11. 2, 1, 2, 1
12. 1, 2, 2, 1
13. 2, 3, 6, 1
14. 1, 2, 1, 2
15. 2, 3, 6, 1
16. 2, 1, 2
17. 2, 6, 3, 2
18. 1, 3, 2
19. 1, 2, 1, 2
20. 2, 1, 1