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When an Alkali Metal Dissolves in Liquid Ammonia the Solution Can Acquire Different Colours. Explain the Reasons for this Type of Colour Change. - CBSE (Science) Class 11 - Chemistry

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Question

When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.

Solution 1

When an alkali metal is dissolved in liquid ammonia, it results in the formation of a deep blue coloured solution.

`M +(x+y) NH_3 -> M^(+)(NH_3)_x  + e^(-1)(NH_3)_y`

The ammoniated electrons absorb energy corresponding to red region of visible light. Therefore, the transmitted light is blue in colour.

At a higher concentration (3 M), clusters of metal ions are formed. This causes the solution to attain a copper–bronze colour and a characteristic metallic lustre.

Solution 2

Alkali metals dissolve in liquid ammonia and give deep blue solutions which are conducting in nature because ammoniated electrons absorb energy in the visible region of light and impart blue colour.

`M + (x + y) NH_3 -> [M(NH_3)_x]^+ + e^(-)(NH_3)_y`

                                                       Ammoniated electrons

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 NCERT Solution for Chemistry Textbook for Class 11 (2018 to Current)
Chapter 10: The s-Block Elements
Q: 10 | Page no. 305
Solution When an Alkali Metal Dissolves in Liquid Ammonia the Solution Can Acquire Different Colours. Explain the Reasons for this Type of Colour Change. Concept: Group 1 Elements - Alkali Metals.
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