Balancing Chemical Equation activity - Free Printable

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

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1. N₂ + H₂ → NH₃

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

We need to make N and H equal on both sides.

Try putting a 2 in front of NH₃:
→ N₂ + H₂ → 2NH₃
Now right has: 2 N, 6 H

So left needs 6 H → put 3 in front of H₂:
→ N₂ + 3H₂ → 2NH₃

Check: Left: 2 N, 6 H | Right: 2 N, 6 H ✔

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2. H₂O → H₂ + O₂

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

Oxygen is unbalanced. Put 2 in front of H₂O:
→ 2H₂O → H₂ + O₂
Left: 4 H, 2 O

Now hydrogen: right has only 2 H → put 2 in front of H₂:
→ 2H₂O → 2H₂ + O₂

Check: Left: 4 H, 2 O | Right: 4 H, 2 O ✔

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3. CH₄ + O₂ → CO₂ + H₂O

Left: 1 C, 4 H, 2 O
Right: 1 C, 2 H, 3 O (1 from CO₂? Wait — CO₂ has 2 O, H₂O has 1 O → total 3 O)

Hydrogen: left has 4 H, right has 2 H → put 2 in front of H₂O:
→ CH₄ + O₂ → CO₂ + 2H₂O
Now right: 1 C, 4 H, 4 O (CO₂ = 2 O, 2H₂O = 2 O → total 4 O)

Left: O₂ gives 2 O → need 4 O → put 2 in front of O₂:
→ CH₄ + 2O₂ → CO₂ + 2H₂O

Check: Left: 1 C, 4 H, 4 O | Right: 1 C, 4 H, 4 O ✔

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4. CO₂ → CO + O₂

Left: 1 C, 2 O
Right: 1 C, 3 O (CO has 1 O, O₂ has 2 O → total 3 O)

Not balanced. Try 2 CO₂ on left:
→ 2CO₂ → CO + O₂
Left: 2 C, 4 O

Right: need 2 C → put 2 in front of CO:
→ 2CO₂ → 2CO + O₂
Now right: 2 C, 2 O (from 2CO) + 2 O (from O₂) = 4 O ✔

Check: Left: 2 C, 4 O | Right: 2 C, 4 O ✔

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5. CH₂O + H₂ → CH₃OH

Left: C=1, H=2+2=4, O=1
Right: C=1, H=4, O=1 → already balanced!

Wait — let’s count again:

CH₂O: C=1, H=2, O=1
H₂: H=2 → total H = 4
CH₃OH: C=1, H=4 (3+1), O=1 → yes, same.

So coefficients are all 1.

→ 1CH₂O + 1H₂ → 1CH₃OH ✔

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6. P₄ + H₂ → PH₃

Left: P=4, H=2
Right: P=1, H=3

Need 4 P on right → put 4 in front of PH₃:
→ P₄ + H₂ → 4PH₃
Right: 4 P, 12 H

Left: H₂ has 2 H → need 12 H → put 6 in front of H₂:
→ P₄ + 6H₂ → 4PH₃

Check: Left: 4 P, 12 H | Right: 4 P, 12 H ✔

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7. C + O₂ → CO₂

Left: C=1, O=2
Right: C=1, O=2 → already balanced!

→ 1C + 1O₂ → 1CO₂ ✔

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8. HCl → H₂ + Cl₂

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

Put 2 in front of HCl:
→ 2HCl → H₂ + Cl₂

Check: Left: 2 H, 2 Cl | Right: 2 H, 2 Cl ✔

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Final Answer:

1. 1 N₂ + 3 H₂ → 2 NH₃
2. 2 H₂O → 2 H₂ + 1 O₂
3. 1 CH₄ + 2 O₂ → 1 CO₂ + 2 H₂O
4. 2 CO₂ → 2 CO + 1 O₂
5. 1 CH₂O + 1 H₂ → 1 CH₃OH
6. 1 P₄ + 6 H₂ → 4 PH₃
7. 1 C + 1 O₂ → 1 CO₂
8. 2 HCl → 1 H₂ + 1 Cl₂