Answer: CaO·SiO 2 ·Al 2 O 3 (calcium aluminosilicate).
- A CaO·SiO<sub>2</sub>·Al<sub>2</sub>O<sub>3</sub> (calcium aluminosilicate)
- B Pure CaCO<sub>3</sub> with no other mineral components present
- C Ca(OH)<sub>2</sub> alone, used directly without further processing
- D CaSO<sub>4</sub>, the same hemihydrate used in plaster of Paris
Correct answer: A. CaO·SiO<sub>2</sub>·Al<sub>2</sub>O<sub>3</sub> (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.