Worksheet for practicing balancing chemical equations with step-by-step guidance.

Let’s go step by step to balance each chemical equation. Remember: atoms are not created or destroyed in a reaction — so the number of each type of atom on the left (reactants) must equal the number on the right (products). We do this by adding coefficients (numbers in front of formulas), never changing subscripts!

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Try these:

#### 1. Ca + O₂ → CaO

Left:
- Ca = 1
- O = 2

Right:
- Ca = 1
- O = 1

→ Oxygen is unbalanced. Let’s put a 2 in front of CaO:
Ca + O₂ → 2CaO

Now right side has:
- Ca = 2
- O = 2

Left still has Ca = 1 → Put a 2 in front of Ca:
2Ca + O₂ → 2CaO

Check:
Left: Ca=2, O=2
Right: Ca=2, O=2 ✔ Balanced!

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#### 2. N₂ + H₂ → NH₃

Left:
- N = 2
- H = 2

Right:
- N = 1
- H = 3

We need same N and H on both sides.

Start with nitrogen: Right has 1 N per NH₃, left has 2 N → put 2 in front of NH₃:
N₂ + H₂ → 2NH₃

Now right: N=2, H=6
Left: N=2, H=2 → Need 6 H on left → H₂ has 2 H per molecule → need 3 H₂ molecules:
N₂ + 3H₂ → 2NH₃

Check:
Left: N=2, H=6
Right: N=2, H=6 ✔ Balanced!

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#### 3. Cu₂O + C → Cu + CO₂

Left:
- Cu = 2
- O = 1
- C = 1

Right:
- Cu = 1
- C = 1
- O = 2

Copper and oxygen are off.

First, fix copper: Left has 2 Cu, right has 1 → put 2 in front of Cu:
Cu₂O + C → 2Cu + CO₂

Now check oxygen: Left = 1, Right = 2 → Not balanced.

Carbon is okay for now (1 each side).

To get 2 oxygen on left, we need 2 Cu₂O? But that gives 4 Cu...

Try:
2Cu₂O + C → ?

Left: Cu=4, O=2, C=1
Right: If we make 4 Cu and 1 CO₂ → Cu=4, C=1, O=2 → Perfect!

So:
2Cu₂O + C → 4Cu + CO₂

Check:
Left: Cu=4, O=2, C=1
Right: Cu=4, C=1, O=2 ✔ Balanced!

Wait — let me double-check original problem: It says “Cu₂O + C → Cu + CO₂”

Yes, so our answer is correct.

But wait — sometimes people write it differently. Let me verify again:

Original: Cu₂O + C → Cu + CO₂

After balancing:
2Cu₂O + C → 4Cu + CO₂

Atoms:
Left: Cu=4, O=2, C=1
Right: Cu=4, C=1, O=2 → Yes, balanced.

✔ Correct.

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#### 4. H₂O₂ → H₂O + O₂

This one is decomposition.

Left:
- H = 2
- O = 2

Right:
- H = 2 (in H₂O)
- O = 1 (in H₂O) + 2 (in O₂