Types of Chemical Reactions Worksheets - Free Printable - Free Printable

Let’s go step by step to solve each problem.

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Part A: Classify the reactions

We need to match each reaction to one of these types:
- Synthesis: Two or more things combine to make one product. (A + B → AB)
- Decomposition: One thing breaks into two or more products. (AB → A + B)
- Single-replacement: One element replaces another in a compound. (A + BC → AC + B)
- Double-replacement: Two compounds swap parts. (AB + CD → AD + CB)
- Combustion: A hydrocarbon reacts with oxygen to make CO₂ and H₂O. (CxHy + O₂ → CO₂ + H₂O)

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1) Al₂(SO₄)₃ + 3 BaCl₂ → 3 BaSO₄ + 2 AlCl₃
→ Two compounds are swapping ions: Al pairs with Cl, Ba pairs with SO₄.
✔ Double-replacement

2) Al₂S₃ → 2 Al + 2 S
→ One compound breaks into its elements.
✔ Decomposition

3) 2 NaOH + CuSO₄ → Na₂SO₄ + Cu(OH)₂
→ Sodium swaps with copper — Na goes with SO₄, Cu goes with OH.
✔ Double-replacement

4) Fe + H₂SO₄ → FeSO₄ + H₂
→ Iron replaces hydrogen in the acid.
✔ Single-replacement

5) C₄H₁₂ + 7 O₂ → 4 CO₂ + 6 H₂O
→ Hydrocarbon + oxygen → carbon dioxide + water. Classic combustion.
✔ Combustion

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Part B: Balance equations AND classify type

We’ll balance first, then classify.

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1) H₂S + O₂ → SO₂ + H₂O

Left: H=2, S=1, O=2
Right: H=2, S=1, O=3 (2 from SO₂ + 1 from H₂O) → not balanced.

Try putting 2 in front of H₂S and 2 in front of H₂O:

2 H₂S + O₂ → SO₂ + 2 H₂O
Now H: left=4, right=4 ✔
S: left=2, right=1 ✘ → put 2 in front of SO₂:

2 H₂S + O₂ → 2 SO₂ + 2 H₂O
Now S: 2=2 ✔
H: 4=4 ✔
O: left=2, right= (2×2)+(2×1)=4+2=6 ✘ → so we need 3 O₂ on left:

2 H₂S + 3 O₂ → 2 SO₂ + 2 H₂O
Check O: left=6, right=4+2=6 ✔
Balanced!

Type: This is a fuel (H₂S) burning in oxygen → makes CO₂? Wait, no carbon here. But it’s still a reaction with O₂ producing oxides → often called combustion even if not hydrocarbon. But technically, since it’s not a hydrocarbon, some might call it oxidation. However, in many school contexts, any reaction with O₂ producing oxides is labeled combustion. Let’s check products: SO₂ and H₂O — yes, similar pattern.
✔ Combustion

*(Note: Some curricula may label this as “oxidation” but for standard classification at this level, combustion is acceptable.)*

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2) C₅H₉O + O₂ → CO₂ + H₂O

This looks like a combustion reaction (organic compound + O₂ → CO₂ + H₂O). Let’s balance.

Assume: C₅H₉O + x O₂ → 5 CO₂ + y H₂O

Carbon: 5 on left → 5 CO₂ on right ✔
Hydrogen: 9 on left → so y = 9/2 → use fractions temporarily.

C₅H₉O + x O₂ → 5 CO₂ + (9/2) H₂O

Now count oxygen:

Left: 1 (from C₅H₉O) + 2x
Right: 5×2 + (9/2)×1 = 10 + 4.5 = 14.5

So: 1 + 2x = 14.5 → 2x = 13.5 → x = 6.75

Multiply entire equation by 4 to eliminate decimals:

4 C₅H₉O + 27 O₂ → 20 CO₂ + 18 H₂O

Check:

C: 4×5=20, right=20 ✔
H: 4×9=36, right=18×2=36 ✔
O: left=4×1 + 27×2 = 4 + 54 = 58
right=20×2 + 18×1 = 40 + 18 = 58 ✔

Balanced!

Type: Organic compound + O₂ → CO₂ + H₂O → classic combustion.
✔ Combustion

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3) Al + NiBr₂ → AlBr₃ + Ni

Left: Al=1, Ni=1, Br=2
Right: Al=1, Br=3, Ni=1 → Br not balanced.

Find LCM of 2 and 3 → 6.

Put 3 in front of NiBr₂ → gives 6 Br
Put 2 in front of AlBr₃ → gives 6 Br

So: Al + 3 NiBr₂ → 2 AlBr₃ + Ni

Now Ni: left=3, right=1 → put 3 in front of Ni

Al: left=1, right=2 → put 2 in front of Al

Final: 2 Al + 3 NiBr₂ → 2 AlBr₃ + 3 Ni

Check:
Al: 2=2 ✔
Ni: 3=3 ✔
Br: 3×2=6, 2×3=6 ✔

Type: Aluminum replaces nickel in the compound → single replacement.
✔ Single-replacement

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4) Al + O₂ → Al₂O₃

Left: Al=1, O=2
Right: Al=2, O=3

LCM for O: 6 → so 3 O₂ and 2 Al₂O₃

But let’s do properly:

Put 2 in front of Al₂O₃ → needs 4 Al and 6 O

So right: 4 Al, 6 O

Left: O₂ → need 3 O₂ to get 6 O
Al → need 4 Al

So: 4 Al + 3 O₂ → 2 Al₂O₃

Check: Al: 4=4, O: 6=6 ✔

Type: Two elements combining to form one compound → synthesis.
✔ Synthesis

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5) H₂O₂ → H₂ + O₂

Left: H=2, O=2
Right: H=2, O=2 → already balanced?

Wait: H₂O₂ → H₂ + O₂

Atoms: H:2=2, O:2=2 → yes, balanced as written.

But is that correct chemically? Actually, hydrogen peroxide decomposes to water and oxygen, not hydrogen gas. But according to the equation given, it says H₂ + O₂.

If we take the equation literally: H₂O₂ → H₂ + O₂ — atoms balance.

But in reality, this reaction doesn’t happen that way — it should be 2 H₂O₂ → 2 H₂O + O₂. However, the problem gives us H₂O₂ → H₂ + O₂, and asks to balance it.

As written: H₂O₂ → H₂ + O₂ — already balanced.

Type: One compound breaking into two elements → decomposition.
✔ Decomposition

*(Note: In real chemistry, this isn't accurate, but for the purpose of this worksheet, we follow what's given.)*

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Final Answers:

Part A:
1) Double-replacement
2) Decomposition
3) Double-replacement
4) Single-replacement
5) Combustion

Part B:
1) 2 H₂S + 3 O₂ → 2 SO₂ + 2 H₂O — Combustion
2) 4 C₅H₉O + 27 O₂ → 20 CO₂ + 18 H₂O — Combustion
3) 2 Al + 3 NiBr₂ → 2 AlBr₃ + 3 Ni — Single-replacement
4) 4 Al + 3 O₂ → 2 Al₂O₃ — Synthesis
5) H₂O₂ → H₂ + O₂ — Decomposition *(already balanced)*

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Final Answer:
Part A:
1) Double-replacement
2) Decomposition
3) Double-replacement
4) Single-replacement
5) Combustion

Part B:
1) 2 H₂S + 3 O₂ → 2 SO₂ + 2 H₂O — Combustion
2) 4 C₅H₉O + 27 O₂ → 20 CO₂ + 18 H₂O — Combustion
3) 2 Al + 3 NiBr₂ → 2 AlBr₃ + 3 Ni — Single-replacement
4) 4 Al + 3 O₂ → 2 Al₂O₃ — Synthesis
5) H₂O₂ → H₂ + O₂ — Decomposition