Types of Reactions

Types of Reactions?

The main reaction types are: synthesis, decomposition, single replacement, double replacement, and combustion.

Synthesis reaction

A reaction where two or more substances combine to form ONE product; general form: A + B → AB

Decomposition reaction

A reaction in which ONE reactant breaks down into two or more simpler products; general form: AB → A + B

How to recognize a synthesis reaction

Look at the product side; if there is just one singular product with no plus signs (+) then it’s synthesis

How to recognize a decomposition reaction

Look at the reactant side; if there is just one reactant with no plus signs (+) breaking into multiple products, it’s decomposition

Real world example of synthesis

2Mg + O₂ → 2MgO (Magnesium oxide = MgO)

Real world example of decomposition

2H₂O₂ → 2H₂O + O₂ (Hydrogen peroxide = H₂O₂)

Single Replacement Reaction

An element and a compound react; the element replaces part of the compound; A + BC → AC + B

Double Replacement Reaction

Two compounds react and swap partners; AB + CD → AD + CB

Why CB and not BC in Double Replacement Reactions?

Cation (positive) is always written first, anion (negative) always written last in any formula

How to recognize single replacement

One element + one compound on both sides

How to recognize double replacement

Two compounds on both sides, no free elements

Real world example of single replacement

Zn + 2HCl → ZnCl₂ + H₂

Real world example of double replacement

2KI + Pb(NO₃)₂ → 2KNO₃ + PbI₂

Combustion reaction

A high-speed chemical process where a fuel combines with oxygen to release energy as heat and light

What is the general formula for combustion?

C_xH_y + O₂ → H₂O + CO₂

How can you tell if a reaction is (complete) combustion?

If there is oxygen (O₂) on the reactant side AND water (H₂O) and carbon dioxide (CO₂) on the product side.