Answer: Dissolution of alkali metals in liquid NH 3 to give blue solutions (solvated electrons).
- A Dissolution of alkali metals in liquid NH<sub>3</sub> to give blue solutions (solvated electrons)
- B The direct formation of sodium peroxide from sodium metal and oxygen during normal conditions
- C The electrolytic reduction of molten calcium chloride to calcium metal as generally observed
- D The Solvay process used to manufacture sodium carbonate in typical laboratory settings
Correct answer: A. Dissolution of alkali metals in liquid NH<sub>3</sub> to give blue solutions (solvated electrons)
Explanation: Alkali metals dissolve in liquid NH<sub>3</sub>: Na → Na+ + e-(solvated), giving blue paramagnetic solutions. At higher concentrations they turn bronze (metallic) and conduct electricity.
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.