All alkali metals dissolve in anhydrous liquid ammonia to give blue colour solution. It is the ammoniated electron which is responsible for the blue colour of the solution, and the electrical conductivity is mainly due to ammoniated electron, [e(NH 3 ) y ] – . Dilute solutions are paramagnetic due to free ammoniated electrons ; this paramagnetism decreases at higher concentration. Above 3M concentration, the solutions are diamagnetic and no longer blue but are bronze/copper-bronze coloured with a metallic luster.
(i) Which of the following changes will be observed in concentrated solution of alkali metal in liquid ammonia ?
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(i) Above 3M concentration, the solutions are no longer blue but are bronze/copper-bronze coloured with a metallic luster. Greater concentration of electrons per unit volume increases the reducing power.
(ii) The dilute solutions conduct electricity better than any salt in any liquid and the conductivity is similar to that of the pure metals. Conduction is due mainly to the presence of solvated electrons.
The dilute solutions are paramagnetic but this paramagnetism decreases at higher concentration. As the concentration of metal increases, metal ion clusters are formed and above 3M concentration the solutions are diamagnetic.
Ammoniated electrons are responsible for the blue colour of the solution.
(iii) The dilute solutions have strong reducing properties on account of the presence of solvated unpaired electrons.
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