Answer: Sodium carbonate (Na 2 CO 3 ).
- A Sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>)
- B Sodium chloride
- C Sodium hydroxide
- D Sodium bicarbonate only
Correct answer: A. Sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>)
Explanation: The Solvay (ammonia-soda) process produces sodium carbonate from salt, ammonia, and CO<sub>2</sub>.
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.