Q1. [1] straightforward thorough-understanding
Which of the following correctly identifies both the energy input and the type of decomposition in the reaction: CaCO₃(s) → CaO(s) + CO₂(g)?
(A) Electrical energy; electrolytic decomposition
(B) Heat energy; thermal decomposition
(C) Light energy; photochemical decomposition
(D) Heat energy; double displacement reaction
- A Electrical energy; electrolysis
- B Heat energy; thermal decomposition
- C Light energy; photolysis
- D Heat energy; combination reaction
Generated by claude-sonnet-4-6 · 2026-06-26 00:54 · grounding rag
Model Answer
(B) Heat energy; thermal decomposition
CaCO₃ is heated strongly to decompose into CaO and CO₂. This is thermal decomposition — a single substance breaks down using heat energy.
Explanation
- The reaction requires high temperature (heat energy), ruling out options A (electrical) and C (light).
- It is a decomposition reaction (one reactant → two products), not a combination or double displacement, ruling out option D.
- Key term to remember: decomposition using heat = thermal decomposition. Classic CBSE example: CaCO₃ → CaO + CO₂.