Answer: Recovered and recycled by treating NH4Cl with Ca(OH)2.
- A Recovered and recycled by treating NH4Cl with Ca(OH)2
- B Discharged entirely as waste gas at the end of the process
- C Permanently consumed and converted into sodium bicarbonate
- D Reduced back to elemental nitrogen gas for disposal
Correct answer: A. Recovered and recycled by treating NH4Cl with Ca(OH)2
Explanation: NH4Cl produced is treated with Ca(OH)2 (slaked lime) to recover ammonia: 2NH4Cl + Ca(OH)2 → CaCl2 + 2NH3 + 2H2O.
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.