Answer: CaO·SiO2·Al2O3 (calcium aluminosilicate).
- A CaO·SiO2·Al2O3 (calcium aluminosilicate)
- B Pure CaCO3 with no other mineral components present
- C Ca(OH)2 alone, used directly without further processing
- D CaSO4, the same hemihydrate used in plaster of Paris
Correct answer: A. CaO·SiO2·Al2O3 (calcium aluminosilicate)
Explanation: Portland cement is a mixture of calcium silicates and aluminates formed by sintering limestone with clay.
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.