Which characteristic best identifies a decomposition reaction?

Decomposition reaction = Those reactions in which single compound decompose down to give two or more products are called decomposition reaction .

Explanation:

Those reactions in which single compound decompose down to give two or more products are called decomposition reaction .

For the Decomposition reaction to take place , a large amount of energy ias needed. This is because for decomposition bonds are required to breaks. Hence energy is needed to break the bonds as they have strong force of attraction.

They occur in presence of HEAT , LIGHT , ELECTRICITY.

examples of decomposition reactions are:

Here only one CaCO3 is producing two substances which are : CaO and CO2

This is also known as decompositon of Calcium carbonate and it require a lot of heat energy.

This is also a decomposition reaction , This occur in the presence of sunlight

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.