Decomposition - Chemistry

1. Fundamental Concepts

Definition:

A chemical reaction in which a single compound breaks down into two or more simpler substances.

General Equation: $AB \rightarrow A + B$

Energy Requirement:

Most decomposition reactions require an input of energy (heat, light, or electricity) to break chemical bonds and are therefore endothermic.

2. Key Concepts

Electrolysis: Decomposition using an electric current (e.g., water).

Thermal Decomposition: Decomposition caused by heating a compound.

Photodecomposition: Decomposition caused by light energy (e.g., silver chloride in sunlight).

Binary Compounds: Compounds made of two elements may decompose into simpler substances, sometimes including their constituent elements, under appropriate conditions.

3. Examples

Easy

$2H_2O(l) \rightarrow 2H_2(g) + O_2(g)$

Water decomposes into hydrogen and oxygen through electrolysis.

Medium

$CaCO_3(s) \xrightarrow{\Delta} CaO(s) + CO_2(g)$

Calcium carbonate decomposes when heated.

4. Problem-Solving Techniques

Identify Reactants and Products: Clearly identify the starting compound and the resulting simpler substances.
Balance the Equation: Ensure the number of atoms of each element is the same on both sides of the equation.
Check for Energy Input: Determine if the reaction requires heat, light, or electricity and include it in the equation.
Use Subscripts and Coefficients Correctly: Use subscripts to indicate the number of atoms in a molecule and coefficients to balance the equation.