Answer: Recovered and recycled by treating NH 4 Cl with Ca(OH) 2.
- A Recovered and recycled by treating NH<sub>4</sub>Cl with Ca(OH)<sub>2</sub>
- 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 NH<sub>4</sub>Cl with Ca(OH)<sub>2</sub>
Explanation: NH<sub>4</sub>Cl produced is treated with Ca(OH)<sub>2</sub> (slaked lime) to recover ammonia: 2NH<sub>4</sub>Cl + Ca(OH)<sub>2</sub> → CaCl<sub>2</sub> + 2NH<sub>3</sub> + 2H<sub>2</sub>O.
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.