NCERT Class XI Chemistry The s-Block Elements Solutions
© examsnet.com
Question : 10
Total: 32
When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
Solution:
The alkali metals dissolve in liq. N H 3
The colour of the dilute solution is blue. The metal atom loses an electron and it combines with ammonia molecule.
M + (x + y)N H 3 [ M ( N H 3 ) x ] + + [ e ( N H 3 ) y ] –
The blue colour of the solution is due to the ammoniated electron which absorbs energy in the visible region of light and thus, imparts blue colour to the solution. The solutions are paramagnetic and on standing, slowly they liberate hydrogen resulting in the formation of an amide.
M ( a m ) + + e ( a m ) − + N H 3 ( l ) M N H 2 ( a m ) +
H 2
am = solution in ammonia
In concentrated solution, the blue colour changes to bronze and becomes diamagnetic.
The colour of the dilute solution is blue. The metal atom loses an electron and it combines with ammonia molecule.
M + (x + y)
The blue colour of the solution is due to the ammoniated electron which absorbs energy in the visible region of light and thus, imparts blue colour to the solution. The solutions are paramagnetic and on standing, slowly they liberate hydrogen resulting in the formation of an amide.
am = solution in ammonia
In concentrated solution, the blue colour changes to bronze and becomes diamagnetic.
© examsnet.com
Go to Question: