49 Balancing Chemical Equations Worksheets [with Answers] - Free Printable

Let's go through the Balancing Chemical Equations Worksheet step by step and solve each part with clear explanations.

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Part 1: Identify Subscripts and Coefficients

Instructions:
1. Draw a circle around each subscript.
2. Draw a square around each coefficient.

We are given:

- H₂O
- 5Cl₂
- 2Mg
- 3H₂O₂

#### Step-by-step breakdown:

| Expression | Subscripts (circle) | Coefficients (square) |
|-----------|----------------------|------------------------|
| H₂O | Circle around 2 (in H₂), and 1 (implied in O, but usually not written) → so just 2 is circled | No coefficient (so no square) |
| 5Cl₂ | Circle around 2 (in Cl₂) | Square around 5 |
| 2Mg | No subscript (Mg has no number after it) → no circle | Square around 2 |
| 3H₂O₂ | Circle around 2 (in H₂), 2 (in O₂) | Square around 3 |

> ✔ Answer for Part 1:
>
> - H₂O → Circle: ₂; No square
> - 5Cl₂ → Circle: ₂, Square: 5
> - 2Mg → No circle, Square: 2
> - 3H₂O₂ → Circles: ₂ (H), ₂ (O); Square: 3

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Part 2: List Elements and Count Atoms

For each compound:
1. List chemical symbols of elements.
2. Give number of atoms of each element.

#### 1. HCl
- Elements: H, Cl
- Number of atoms:
- H: 1
- Cl: 1

✔ Answer:
- Elements: H, Cl
- Atoms: H = 1, Cl = 1

#### 2. CO₂
- Elements: C, O
- Number of atoms:
- C: 1
- O: 2 (from subscript)

✔ Answer:
- Elements: C, O
- Atoms: C = 1, O = 2

#### 3. Na₂SO₄
- Elements: Na, S, O
- Number of atoms:
- Na: 2 (from subscript)
- S: 1 (no subscript → implied 1)
- O: 4 (from subscript)

✔ Answer:
- Elements: Na, S, O
- Atoms: Na = 2, S = 1, O = 4

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Part 3: Balance the Chemical Equations

We will balance each equation using the law of conservation of mass: same number of atoms of each element on both sides.

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#### 1. ___ Cu₂O + ___ C → ___ Cu + ___ CO₂

Step 1: Count atoms on each side

Unbalanced:
- Left: Cu₂O → 2 Cu, 1 O; C → 1 C
- Right: Cu → 1 Cu; CO₂ → 1 C, 2 O

So total left: Cu=2, O=1, C=1
Right: Cu=1, C=1, O=2 → Not balanced.

Strategy:
- We need to balance O and Cu.

Notice:
- CO₂ has 2 O, but Cu₂O only has 1 O per molecule → we need even number of O atoms.
- Let’s try 2 Cu₂O → gives 4 Cu and 2 O
- Then 1 CO₂ needs 2 O → perfect.

So:
- 2 Cu₂O → 4 Cu, 2 O
- 1 C → 1 C
- Products: 4 Cu, 1 CO₂ (which has 1 C and 2 O)

Now check:
- Left: Cu = 4, O = 2, C = 1
- Right: Cu = 4, C = 1, O = 2 → Balanced!

✔ So the balanced equation is:

2 Cu₂O + 1 C → 4 Cu + 1 CO₂

But we can write coefficients as whole numbers without "1" if possible. But here, all are needed.

Final answer:
2 Cu₂O + C → 4 Cu + CO₂

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#### 2. ___ H₂O₂ → ___ H₂O + ___ O₂

This is decomposition of hydrogen peroxide.

Unbalanced:
- Left: H₂O₂ → 2 H, 2 O
- Right: H₂O → 2 H, 1 O; O₂ → 2 O

Total right: H=2, O=3 → not balanced.

We need equal H and O.

Try 2 H₂O₂ → gives 4 H, 4 O

Then:
- Make 2 H₂O → uses 4 H and 2 O
- Remaining O: 4 – 2 = 2 → makes 1 O₂

So:
- Left: 2 H₂O₂ → 4 H, 4 O
- Right: 2 H₂O → 4 H, 2 O; 1 O₂ → 2 O → total 4 H, 4 O

✔ Balanced!

Answer:
2 H₂O₂ → 2 H₂O + O₂

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#### 3. ___ Al + ___ Fe₃N₂ → ___ AlN + ___ Fe

Unbalanced:
- Left: Al, Fe₃N₂ → 3 Fe, 2 N
- Right: AlN → 1 Al, 1 N; Fe → 1 Fe

Need to balance Fe, N, and Al.

Look at Fe₃N₂ → has 3 Fe and 2 N → so we need products to have multiples of these.

Let’s assume we use 1 Fe₃N₂ → gives 3 Fe and 2 N

To get 2 N on right, we need 2 AlN → gives 2 Al and 2 N

Then Fe: 3 Fe → need 3 Fe on right → so 3 Fe

Al: 2 Al from 2 AlN → so need 2 Al on left

So:
- Left: 2 Al + 1 Fe₃N₂
- Right: 2 AlN + 3 Fe

Check atoms:
- Left: Al = 2, Fe = 3, N = 2
- Right: Al = 2, N = 2, Fe = 3 → ✔ Balanced!

Answer:
2 Al + Fe₃N₂ → 2 AlN + 3 Fe

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✔ Final Answers:

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Part 1: Subscripts and Coefficients

- H₂O → Circle: ₂
- 5Cl₂ → Circle: ₂, Square: 5
- 2Mg → Square: 2
- 3H₂O₂ → Circles: ₂ (H), ₂ (O); Square: 3

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Part 2: Elements and Atom Counts

| Compound | Elements | Atoms |
|--------|---------|-------|
| HCl | H, Cl | H = 1, Cl = 1 |
| CO₂ | C, O | C = 1, O = 2 |
| Na₂SO₄ | Na, S, O | Na = 2, S = 1, O = 4 |

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Part 3: Balanced Equations

1. 2 Cu₂O + C → 4 Cu + CO₂
2. 2 H₂O₂ → 2 H₂O + O₂
3. 2 Al + Fe₃N₂ → 2 AlN + 3 Fe

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📌 Summary Explanation:

- Subscripts tell how many atoms of an element are in one molecule (e.g., H₂O has two H).
- Coefficients tell how many molecules or moles of a substance are involved (e.g., 2H₂O means two water molecules).
- When balancing equations, adjust coefficients, never change subscripts.
- Always check that atoms of each element are equal on both sides.

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