C

Combination Reaction

A + B → AB (synthesis); e.g., 2Mg + O₂ → 2MgO
Quick Reference
Formula / NotationA + B → AB (synthesis); e.g., 2Mg + O₂ → 2MgO
Also Known AsSynthesis reaction, direct combination reaction, addition reaction (general sense)

What is Combination Reaction?

A combination reaction (synthesis reaction) is a reaction in which two or more substances combine to form a single product. The general form is A + B → AB. Examples include iron reacting with sulfur (Fe + S → FeS), hydrogen burning in oxygen (2H₂ + O₂ → 2H₂O), and the formation of sulfur trioxide (2SO₂ + O₂ → 2SO₃).

Formula & Notation

A + B → AB (synthesis); e.g., 2Mg + O₂ → 2MgO

Other Names / Synonyms: Synthesis reaction, direct combination reaction, addition reaction (general sense)

Properties & Characteristics

A combination reaction (synthesis reaction) is one in which two or more substances combine to form a single new product. The reactants can be elements or compounds. Combination reactions are often highly exothermic (e.g., metal combustion, oxide formation). They are the reverse of decomposition reactions. The product has different properties from the reactants.

Uses & Applications

Combination reactions are fundamental in industrial synthesis: formation of ammonia (N₂ + 3H₂ → 2NH₃, Haber process), sulfur trioxide (2SO₂ + O₂ → 2SO₃, Contact process), iron oxide (rusting), and the synthesis of ionic compounds by direct combination of elements.

Safety Information

Many combination reactions between elements are highly exothermic and may be explosive or pyrophoric. Mixing reactive elements (e.g., hydrogen and fluorine, phosphorus and chlorine) must be done with extreme caution. Always add in small quantities and assess heat of reaction.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Combination Reaction
Formula A + B → AB (synthesis); e.g., 2Mg + O₂ → 2MgO
Synonyms Synthesis reaction, direct combination reaction, addition reaction (general sense)

Frequently Asked Questions

A combination reaction (synthesis reaction) is a reaction in which two or more substances combine to form a single product. The general form is A + B → AB. Examples include iron reacting with sulfur (Fe + S → FeS), hydrogen burning in oxygen (2H₂ + O₂ → 2H₂O), and the formation of sulfur trioxide (2SO₂ + O₂ → 2SO₃).

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