🎓 Prepared by students from Boğaziçi University

What Are the Types of Chemical Reactions?

Chemical reactions are classified into five main types based on how reactants rearrange. Each type follows a unique pattern: synthesis (combination), decomposition, combustion, single displacement, and double displacement. Understanding these categories helps predict reaction products.

Short answer

The five main types are: (1) synthesis (A + B → AB), (2) decomposition (AB → A + B), (3) combustion (fuel + O₂ → products), (4) single displacement (A + BC → AC + B), and (5) double displacement (AB + CD → AD + CB).

Five Types of Chemical Reactions

1
Synthesis
Two or more reactants combine to form one product (A + B → AB)
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2
Decomposition
One reactant breaks into two or more products (AB → A + B)
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3
Combustion
Fuel reacts with oxygen, releasing energy (C + O₂ → CO₂)
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4
Single Displacement
One element replaces another in a compound (A + BC → AC + B)
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5
Double Displacement
Two compounds exchange ions (AB + CD → AD + CB)

Step-by-step worked examples

Classify: 2H₂ + O₂ → 2H₂O

Two reactants (H₂ and O₂) combine into one product (H₂O).
This is a synthesis (combination) reaction.

Classify: 2H₂O₂ → 2H₂O + O₂

One reactant (H₂O₂) breaks into two products (H₂O and O₂).
This is a decomposition reaction.

Classify: CH₄ + 2O₂ → CO₂ + 2H₂O

A fuel (CH₄) reacts with oxygen to produce CO₂ and H₂O.
This is a combustion reaction.

Flashcards

Quick quiz

Q1.Which type: 2H₂ + O₂ → 2H₂O?

Correct answer: B. Two elements combine into one compound — that's synthesis.

Q2.Which reaction breaks one compound into two?

Correct answer: C. Decomposition always breaks one reactant into multiple products.

Q3.C + O₂ → CO₂ is what type?

Correct answer: C. Combustion is burning a fuel in oxygen; this also fits synthesis (elements → compound).

Q4.Fe + CuSO₄ → FeSO₄ + Cu is…?

Correct answer: C. Fe replaces Cu in the compound — single displacement.

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Common mistakes

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Combustion is the same as synthesis. — Correct: Combustion is a subset that always involves oxygen and energy release.

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Single and double displacement are the same. — Correct: Single: one element swaps in/out. Double: two compounds exchange ions.

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Decomposition always produces elements. — Correct: Decomposition produces simpler compounds or elements (e.g., CaCO₃ → CaO + CO₂).

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All reactions fit exactly one category. — Correct: Many reactions fit multiple categories (e.g., combustion + synthesis).

FAQ

What are the five types of chemical reactions?

Synthesis, decomposition, combustion, single displacement, and double displacement.

How do I classify a chemical reaction?

Count reactants and products, check for oxygen, identify which atoms swap. Match to the five types.

Can a reaction be multiple types?

Yes — a combustion reaction is also usually a synthesis (elements/compounds → new compound).

Is burning wood synthesis or combustion?

It's combustion (wood + O₂ → CO₂ + H₂O + heat). Combustion is its own category.