Two or more substances combine to form a single product.
General form:
Example:
Note: This is like mixing ingredients to bake a cake — separate things come together to form one new thing.
A single compound breaks down into two or more simpler substances.
General form:
Example:
Note: Opposite of combination — one thing splits into many. Heat, light, or electricity often drives this type.
One element replaces another element in a compound.
General form:
Example:
Note: The more reactive element always displaces the less reactive one. Refer to the reactivity series!
Two compounds exchange ions to form two new compounds.
General form:
Example:
Note: Think of it as two couples swapping partners. A precipitate, gas, or water is usually formed.
A substance reacts with oxygen to produce heat and light (often forming CO₂ and H₂O).
General form:
Example:
Note: Combustion always requires oxygen. Complete combustion gives CO₂; incomplete gives CO.
An acid reacts with a base to form salt and water.
General form:
Example:
Note: The products are always neutral (pH ≈ 7 for strong acid + strong base). This reaction is exothermic.
Reactions involving transfer of electrons — oxidation is the loss of electrons and reduction is the gain of electrons.
Key rule:
OIL RIG → Oxidation Is Loss, Reduction Is Gain
Example:
In this reaction:
Fe is reduced (gains electrons: Fe³⁺ → Fe⁰)
C is oxidised (loses electrons: C²⁺ → C⁴⁺)
Note: Redox reactions are the basis of electrochemistry, rusting, and biological respiration.
| # | Type | General Form | Key Feature |
|---|---|---|---|
| 1 | Combination | A + B → AB | Multiple → One |
| 2 | Decomposition | AB → A + B | One → Multiple |
| 3 | Single Displacement | A + BC → AC + B | More reactive displaces less reactive |
| 4 | Double Displacement | AB + CD → AD + CB | Ion exchange; precipitate/gas formed |
| 5 | Combustion | Fuel + O₂ → CO₂ + H₂O | Requires O₂; releases energy |
| 6 | Neutralization | Acid + Base → Salt + H₂O | Forms salt and water |
| 7 | Redox | Oxidation + Reduction | Electron transfer (OIL RIG) |
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Types of Chemical Reactions: Combination, Decomposition, Redox & More is a fundamental concept in inorganic chemistry. Understanding the mechanisms, reaction conditions, and stereo-chemical outcomes is crucial for mastering organic chemistry. Our curated resources provide step-by-step visualizations to help you excel.
SELF TEST
What type of reaction is represented by A + B → AB?
LEARNING SUPPORT
You can identify a redox reaction by assigning oxidation numbers to all elements in the reactants and products. If the oxidation number of an element increases, it is oxidized; if it decreases, it is reduced.
A precipitation reaction is a specific type of double displacement reaction where two soluble aqueous salts are mixed, and they react to form an insoluble solid product, which settles out of the solution as a precipitate.
Yes, all combustion reactions are redox reactions. The fuel (usually a hydrocarbon) is oxidized by oxygen, while the oxygen itself is reduced, rapidly releasing energy in the form of heat and light.