Answer: NaHCO3.
- A NaHCO3
- B Na2CO3
- C NaOH
- D Na2SO4
Correct answer: A. NaHCO3
Explanation: Sodium bicarbonate (NaHCO3) 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.