Assertion (A): A reaction in which a single reactant breaks down to give two or more products is called a decomposition reaction.
Reason (R): A decomposition reaction that is not carried out by heating is called thermal decomposition.
Choose the correct option.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (A) is correct but (R) is incorrect.
Assertion (A): A reaction in which a single reactant breaks down to give two or more products is called a decomposition reaction. — Correct. This is the definition of a decomposition reaction; for example, calcium carbonate breaks down into calcium oxide and carbon dioxide on heating.
Reason (R): A decomposition reaction that is not carried out by heating is called thermal decomposition. — Incorrect. Thermal decomposition is decomposition brought about by heat. Decomposition caused by electricity is electrolytic decomposition, and decomposition caused by light is photolytic decomposition.