Answer: Potassium hydrogencarbonate (KHCO3) is too soluble to precipitate out.
- A Potassium does not form a carbonate
- B KCl is insoluble in water
- C Ammonia does not react with potassium salts to form carbonates
- D Potassium hydrogencarbonate (KHCO3) is too soluble to precipitate out
Correct answer: D. Potassium hydrogencarbonate (KHCO3) is too soluble to precipitate out
Explanation: The process relies on the low solubility of NaHCO3 so it precipitates; KHCO3 is appreciably soluble and does not precipitate, so K2CO3 cannot be made this way.
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.