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Consider the following reactions of Group IA (alkali) metals with liquid ammonia: M + (x+y) NH3 -> [M(NH3)ₓ]+ + [e(NH3)_y]- [M(NH3)ₓ]+ + e-(in NH3) -> M-NH2(aq) + (1/2) H2(g) Which of the following statements about these solutions is INCORRECT?

1. The characteristic blue color of dilute solutions arises from ammoniated electrons that absorb radiation in the infrared region of the electromagnetic spectrum
2. On increasing the concentration of the metal, the blue color of the solution changes to a bronze-like metallic color
3. As concentration increases, the solution changes from paramagnetic to diamagnetic
4. The deep blue dilute solution is an electrical conductor

Correct answer: The characteristic blue color of dilute solutions arises from ammoniated electrons that absorb radiation in the infrared region of the electromagnetic spectrum

Solution

The blue color arises because ammoniated electrons absorb in the visible range (not just infrared). Absorption peaks in the near-IR (~1500 nm) and across the red visible region, transmitting blue. Saying it absorbs only in the infrared is an oversimplification that makes the statement misleading/incorrect in the context of what causes the blue color. All other statements are correct.

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