Answer: NaHCO 3.
- A NaHCO<sub>3</sub>
- B Na<sub>2</sub>CO<sub>3</sub>
- C NaOH
- D Na<sub>2</sub>SO<sub>4</sub>
Correct answer: A. NaHCO<sub>3</sub>
Explanation: Sodium bicarbonate (NaHCO<sub>3</sub>) is baking soda, used in baking and as an antacid.
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.