Dilute solutions of alkali metals in liquid `NH_(3)` are blue. It is the ammoniated electron which is responsible for the blue colour of the solution, and the electrical conductivity is due to the ammoniated cation, `[M(NH_(3))_(x)]^(+)` as well as the ammoniated electrons, `[e(NH_(3))_(y)]^(-)`, values of x and y depend on the extent of solvation (by `NH_(3)`). Dilute solutions are paramagnetic due to free electrons.
What happens if alkali metals is allowed to react with concentrated liquid ammonia?

Options

A. Paramagnetic character of solvated electrons is retained
B. Solvated electrons associate to form electron-pairs and paramagnetic character decreases.
C. Reducing character is increased.
D. Reducing character is not affected.

Answer

B

Explanation

`M(s)+NH_(3)("liq.") rarr M^(+). (NH_(3))_(x) + bar(e).(NH_(3))_(y)`
`{:("excess",,"Ammoniated "bar(e)" responsible for"),(,,"blue color & reducing character."):}`
If conc. of solution is increased, then association of solvated electrons get started hence, paramagnetism decreases.