Types of Chemical Reactions

Let’s go over 4 types of chemical reactions.

Synthesis

Decomposition

Single replacement

Double replacement

A synthesis reaction occurs when two or more reactants combine to form a single product. A synthesis reaction can be represented by the general equation:

A + B → C

In this equation, the letters A and B represent the reactants that begin the reaction, and the letter C represents the product that is created or  synthesized in the reaction. The arrow shows the direction in which the reaction occurs. 

An example of a synthesis reaction is the combination of sodium (Na) and chlorine (Cl) to produce salt which is sodium chloride. (NaCl). This reaction is represented by the chemical equation: 2Na + Cl2 → 2NaCl

Another example is the combination of hydrogen and oxygen to create water.

A decomposition reaction occurs when one reactant breaks down into two or more products. It can be represented by the general equation:

AB → A + B

In this equation, AB represents the reactant that begins the reaction, and A and B represent the products of the reaction. The arrow shows the direction in which the reaction occurs.

If you pass an electric current through water it will cause water to decompose. This is an example of a decomposition reaction. Water (H2O) breaks down to produce hydrogen (H2) and oxygen (O2) gasses. The equation for this reaction is as follows.

2 H2O → 2 H2 + O2

A single replacement reaction occurs when one element replaces another in a single compound. This type of reaction has the general equation: 

A + BC → B + AC 

During the reaction, A replaces B, forming the product compound AC 

Here is an example,

Zn(s) + 2HCl (g) yields ZnCl2 ( s) + H2 ( g)

Non-metal hydrogen is displaced by a metal zinc, in order to produce Zinc chloride (ZnCl2) and hydrogen (H2) gas.

A double replacement reaction occurs when two ionic compounds exchange ions. This produces two new ionic compounds. A double replacement reaction can be represented by the general equation:

AB + CD → AD + CB

AB and CD are the two reactant compounds, and AD and CB are the two product compounds that result from the reaction. During the reaction, the ions B and D change places.

In an ionic compound, the positive metal ion is always written first, followed by the negative nonmetal ion. Therefore, A and C must always come first, followed by D or B.

An example of a double replacement reaction is sodium chloride (NaCl) reacting with silver fluoride (AgF). 

NaCl + AgF → NaF + AgCl

During the reaction, chloride and fluoride ions change places, so two new compounds are formed, sodium fluoride (NaF) and silver chloride (AgCl).