Question

Formation of calcium oxide and carbon dioxide by heating limestone is an example of double decomposition reaction.
(A) True
(B) False

Answer 1

Hint: Think about the changes which take place during a decomposition reaction. Find out what is limestone and its molecular formula and write its reaction on action of heat. Find out the difference between decomposition reaction and double decomposition and then draw a conclusion whether the given statement is true or false.


Complete step by step solution:
- Let’s start by defining decomposition and double decomposition reactions.
- A decomposition reaction is a reaction in which one compound decomposes to give two or more simpler products upon action of heat, light or electricity.
- For example, water on action of electricity decomposes to give hydrogen and oxygen gas.
\[{{H}_{2}}O\xrightarrow{Electricity}{{H}_{2}}+{{O}_{2}}\]
- A double decomposition reaction is a reaction in which two compounds react and decompose to give two or more products.
- For example sodium chloride reacts with silver nitrate to form sodium nitrate and silver chloride precipitate.
\[NaCl+AgN{{O}_{3}}\to NaN{{O}_{3}}+AgCl\]
- Now, in the question, the given statement is, limestone undergoes double decomposition to form calcium oxide and carbon-dioxide.
- Limestone is calcium carbonate. Calcium carbonate on action of heat undergoes decomposition to form calcium oxide and carbon dioxide.
\[CaC{{O}_{3}}\to CaO+C{{O}_{2}}\]
- In this reaction, only one reactant decomposes to form two products, calcium oxide and carbon dioxide. Therefore, this reaction is an example of decomposition reaction and not double decomposition reaction.
- Therefore, the given statement, ‘Formation of calcium oxide and carbon dioxide by heating limestone is an example of double decomposition reaction’ is False.

- Therefore, the correct answer is option (B).


Note: Remember that in a decomposition reaction, there is only one reactant. In double decomposition reaction, there are two reactants which react with each other and decompose to form new products. Decomposition of limestone is a decomposition reaction.