Basic Reaction Types

So, we've gone over the basic properties of every chemical reaction and how to balance them. This section will discuss the basic reaction types. The four main reaction types are visualized above, barring combustion. (From top to bottom: Synthesis, Decomposition, Single Displacement, Double Displacement)

A + B → AB

In a synthesis reaction, two separate uncombined reactants react to form a compound product.

AB → A + B

In a decomposition reaction, one compound reactant decomposes into uncombined products.

AB + C → AC + B

In a single displacement reaction, an uncombined reactant replaces an element in a compound.

AB + CD → AD + CB

In a double displacement reaction, two of the elements(usually both an anion or both a cation if the bonds are ionic) switch places. This is common in precipitation reactions.

In a combustion reaction, an element or compound reacts with oxygen gas(O₂) to form a product. Combustion reactions almost always produce heat and/or light. The combustion reaction below is specifically for those that involve hydrocarbons reacting with O₂.

C_xH_y + O₂ → H₂O + CO₂

Every combustion reaction must have O₂ as a reactant but many of the times, the reactant is a hydrocarbon(a compound that involves just carbon and hydrogen and has the form C_xH_y). Whenever a hydrocarbon is involved, the products of the combustion reaction are always carbon dioxide and water vapor. An unbalanced combustion reaction with a hydrocarbon looks like above. The x and y are placeholders for the subscripts of carbon and hydrogen, respectively, in the hydrocarbon.