Answer: CaCO3.
- A CaCO3
- B CaSO4
- C Ca(OH)2
- D CaO
Correct answer: A. CaCO3
Explanation: Limestone is calcium carbonate (CaCO3), a widely used building and industrial material.
Each s-block metal ion emits a characteristic flame colour because heating excites electrons to higher energy levels; light is emitted as they fall back, with the colour determined by the specific energy gap.
Concept context
Group 1 (alkali metals) and Group 2 (alkaline earth metals). Learn their reactions with water and air, important compounds like NaOH, Na₂CO₃, and CaCO₃, and anomalous behaviour of lithium and beryllium.