Answer: Water treatment, mortar, sugar purification.
- A Water treatment, mortar, sugar purification
- B Manufacturing soap through saponification of fats
- C Manufacturing glass by fusing silica with soda ash
- D Industrially producing ammonia from nitrogen and hydrogen
Correct answer: A. Water treatment, mortar, sugar purification
Explanation: Ca(OH)<sub>2</sub> (lime water / milk of lime) is used to soften water, in mortar, to neutralise acidic soil, and to purify cane sugar juice.
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.