Types of Chemical Reactions

Greetings,

This post will discuss the different types of chemical reactions with general equations and specific examples provided.

General Equations of Reaction Types

The common chemical reactions are single-replacement, double-displacement, decomposition, synthesis, and combustion.  It's easy to associate each reaction name with the correct process because the reaction is described by the name.  I will use colored shapes to describe each general reaction type as  shown below.

Arrows were added to the top two reactions to indicate those parts "swapping out".  A variety of shapes and colors were used to make the presentation more interesting and to emphasize the fact that all of these reaction types are very different.  A Synthesis reaction type is also known as a Combination reaction, as indicated above.  The Combustion reaction is displayed using space-filling molecular models for oxygen gas, water and carbon dioxide (the two products).  The other combustion reactant is a general formula for a hydrocarbon molecule with all single bonds between the carbon atoms, of which the single carbon molecule is a special case.  A hydrocarbon compound contains only carbon and hydrogen and the alkane type contains all single bonds. The 'n' and '(2n+2)' subscripts are standard for any hydrocarbon alkane, where 'n' represents the number of carbon atoms in the molecule.  Using the value of 'n' and the general equation coefficients, a balanced equation is obtained.  For even values of 'n' a "half-value" coefficient (a 2 in the denominator) occurs for oxygen gas and it becomes necessary to multiply  the entire equation (meaning every formula coefficient) by '2'.

Specific Reaction Type Examples

The type of a specific reaction is determined by matching the form of the equation with one of the general equations above.  There are specific reaction types which match the different general types.  For instance, a typical single replacement reaction happens when a metal replaces a less active metal in a compound. Common double displacement reactions are precipitation and acid-base.  A decomposition reaction tends to happen when a solid compound can be broken down into one or more gases upon heating.  A common combination reaction is one which produces a compound from its individual elements, such as the combustion of hydrogen gas to produce water.  Some specific examples are listed below.

Specific Examples of Five Common Reaction Types

BaCl₂(aq) + Na₂S(aq) → 2 NaCl(aq) + BaS(S)

HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

Double Displacement

Zn(s) + 2HCl(aq) → H₂(g) + ZnCl₂(aq)

Single Replacement

(NH₄)₂CO₃(s) → 2NH₃(g) + CO₂(g) + H₂O(g)

Decomposition

H₂(g) + O₂(g) → H₂O(g)

Synthesis/Combination

C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g)

Combustion of Propane Gas

The above equations are balanced.  When you study them, you should be able to match each specific example with its reaction-type pattern in the top diagram.  There are very many chemical reactions in Chemistry that fall under the five common types discussed in this post.

That's all for now.

Have a good one!

A Publication of http://www.excellenceinlearning.biz