The Main Types of Chemical Reactions

A chemical reaction may be regarded as the process that occurs when matter undergoes change in composition. To be able to understand chemical reaction, one needs to recognize the key types of reactions. Reaction may be classified in several different ways, namely:

Synthesis (Combination) Reactions; Decomposition Reactions; Substitution (single replacement) Reactions; Precipitation (Double replacement) Reaction; Neutralization (acid-base) Reactions; Redox (Reduction and Oxidation) Reactions;

Type of Reaction Explanation General Equation
(General form change occurrences)
Synthesis/ Combination Reaction in which two or more simpler substances (elements) combine chemically to give a compound. A + B → AB 2H2 + O2 → 2H2O
Decomposition Reaction in which a compound is broken down into simpler substances (elements). AB → A + B 2H2O → 2H2 + O2
Substitution (Single replacement) Reaction in which an atom or group of atoms is replaced by another atom or group. A + BC → AC + B


A + BC → BA + C

Zn + HCl → ZnCl2 + H2


Cl2 + 2NaBr → 2NaCl + Br2

Precipitation (Double replacement) Reaction in which solid compound is formed when solution of two soluble compounds are mixed. AB + CD → AD + CB AgNO3 + NaCl  →  AgCl + NaNO3
Neutralization (acid-base) Reaction in which an acid reacts with a base to give salt and water. HA + BOH → H2O + BA HCl + NaOH → H2O + NaCl


(Reduction- Oxidation)

Reaction which electron transfer occurs. Reduction: A → A + e

Oxidation: B + e → B

Cl2 + 2e → 2Cl (gain electrons)

2Na → Na+ + 2e (loss electrons)

2Na + Cl2 → NaCl