Decomposition Reaction

Table of Contents

Chemical Reactions

A chemical reaction is the process by which one or more substances change into one or more new substances. There are three types of chemical reactions: synthesis, decomposition, and substitution.

In a synthesis reaction, two or more substances combine to form a new chemical compound.
In a decomposition reaction, a chemical compound breaks down into two or more substances.
In a substitution reaction, one atom or group of atoms is replaced by another atom or group of atoms.

Precipitation or Double Replacement Reaction

In a precipitation reaction, two soluble ions react to form a solid compound. The ions come together in a solution, and the solid compound that is formed falls out of the solution. This reaction is also called a double replacement reaction.

In a double replacement reaction, two ions switch places. One ion leaves the solution and one ion joins the solution. This reaction is also called a displacement reaction.

Acid-Base or Neutralization Reaction

When an acid and a base react, they produce a salt and water. The acid and base neutralize each other, and the salt is the result of their reaction.

Oxidation-Reduction or Redox Reactions

Redox reactions are chemical reactions in which atoms have their oxidation state changed. In a redox reaction, one atom loses electrons (oxidation) and another atom gains electrons (reduction).

Redox reactions are important in biology. For example, photosynthesis is a redox reaction in which electrons from water are used to produce glucose.

Combustion Reaction

The combustion reaction of propane is:

C 3 H 8 (g) + 5O 2 (g) → 3CO 2 (g) + 4H 2 O(g)

This equation shows that one mole of propane will produce three moles of carbon dioxide and four moles of water.

Synthesis Reactions

The synthesis of a new molecule from two or more smaller molecules is called a synthesis reaction. In this lesson, we will learn about some specific types of synthesis reactions.

Addition Reactions

In an addition reaction, two small molecules join together to form a larger molecule. The two molecules that join together are called the reactants, and the larger molecule that is formed is called the product.
One common type of addition reaction is the reaction between an alcohol and a hydrogen halide to form an alkyl halide. In this reaction, the alcohol molecule loses a hydrogen atom and the hydrogen halide molecule gains a hydrogen atom.
The reaction between ethanol and hydrogen chloride to form ethyl chloride is an example of an addition reaction.
Another common type of addition reaction is the reaction between an alkene and a hydrogen halide to form an alkyl halide. In this reaction, the alkene molecule loses a hydrogen atom and the hydrogen halide molecule gains a hydrogen atom.
The reaction between ethene and hydrogen chloride to form ethyl chloride is an example of an addition reaction.

A decomposition reaction is a chemical reaction in which one molecule splits into two or more molecules.

Classification of Decomposition Reaction

There are five types of decomposition reaction:

1. Combustion
2. Hydrolysis
3. Decomposition of an ionic compound
4. Decomposition of a covalent compound
5. Decomposition of a complex molecule

1. Thermal Decomposition Reaction

Thermal decomposition reactions are chemical reactions that occur when a substance is heated to the point where it breaks down into two or more simpler substances.

Some common thermal decomposition reactions are the decomposition of water into hydrogen and oxygen, the decomposition of ammonia into nitrogen and hydrogen, and the decomposition of calcium carbonate into calcium oxide and carbon dioxide.

2. Electrolytic Decomposition Reaction:

In an electrolytic decomposition reaction, a compound is broken down into its component elements by the passage of an electric current.

For example, in the electrolysis of water, the water molecule is decomposed into hydrogen and oxygen gas.

3. Photo Decomposition Reaction or Photolysis

This reaction is the decomposition of a molecule into smaller molecules by the absorption of light. The most common example of this is photosynthesis, where light energy is used to convert carbon dioxide and water into glucose and oxygen.

Silver Chloride Decomposition Reaction

Silver chloride decomposes in water to form silver and chlorine gas.

2AgCl(aq) → 2Ag(aq) + Cl2(g)

The chlorine gas can be captured by displacement of water with a water-soluble carbonate, such as sodium carbonate.

2AgCl(aq) → 2Ag(aq) + Cl2(g) + Na2CO3(aq)

Double Decomposition Reaction

A double decomposition reaction is a type of chemical reaction in which two substances react to form two new substances. In a double decomposition reaction, each substance is in a different state of oxidation. For example, in a reaction between potassium chlorate and potassium iodide, potassium chlorate is in the oxidation state of +5 and potassium iodide is in the oxidation state of -1. When they react, potassium chlorate is reduced to potassium chloride (+1) and potassium iodide is oxidized to iodine (+5).

Uses of Decomposition Reaction

There are many uses of decomposition reactions. Some of these include:

Making fertilizer from manure
Making soap from fats and oils
Making ethanol from corn

Importance of Decomposition

Decomposition is important to the environment because it is the process that breaks down dead organic matter and returns the nutrients to the soil. This helps to create new life and maintain the balance of the environment.

Here are Some Tips to Study Decomposition Reaction

1. Understand the types of decomposition reactions.

There are three types of decomposition reactions: thermal decomposition, photo decomposition, and catalyzed decomposition. Thermal decomposition is the most common type and occurs when a chemical reaction takes place in the presence of heat. Photo decomposition is the result of a chemical reaction that takes place when exposed to light. Catalyzed decomposition is a reaction that is sped up by a catalyst.

2. Understand the factors that influence decomposition reactions.

The type of decomposition reaction that takes place is influenced by the nature of the reactants, the temperature, the presence of a catalyst, and the presence of light.

3. Understand the products of decomposition reactions.

The products of a decomposition reaction vary depending on the type of reaction that takes place. Thermal decomposition reactions produce a variety of gases, including hydrogen, carbon monoxide, and carbon dioxide. Photo decomposition reactions produce light and heat, and catalyzed decomposition reactions produce a catalyst.