The alkali metals dissolve in ammonia to give a deep blue solution which is conducting in nature.
`M+(x+y)NH_3rarr[M(NH_3)_x]^(2+)+2[e(NH_3)_y]^(-)` Which of the following is not true about the solutions of alkli metals in liquid ammonia ?

Options

A. The blue colour is due to ammoniated electron
B. The solutions is paramagnetic
C. The blue colour changes to brown on standing
D. In concentrated solution blue colour changes to bronze and becomes diamagnetic

Answer

To solve the question regarding the properties of alkali metals in liquid ammonia, we will analyze the statements provided and determine which one is not true.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
The reaction given is:
\[ M + (x+y)NH_3 \rightarrow [M(NH_3)_x]^{2+} + 2[e(NH_3)_y]^{-} \]
Here, \(M\) represents an alkali metal, and when it dissolves in ammonia, it forms an ammoniated cation and ammoniated electrons.

2. **Color of the Solution**:
The solution of alkali metals in ammonia is known to be deep blue in color. This blue color is attributed to the presence of ammoniated electrons.

3. **Conductivity of the Solution**:
The solution is conducting because alkali metals lose their valence electron easily in ammonia, forming cations and free electrons that can carry charge.

4. **Paramagnetism and Diamagnetism**:
Initially, the solution is paramagnetic due to the presence of unpaired electrons. However, upon standing, the solution becomes diamagnetic as the ammoniated electrons combine with the cations, leading to a change in the magnetic properties.

5. **Color Change Upon Standing**:
The blue color of the solution changes to bronze upon standing. This is due to the changes in the concentration and the interactions of the ammoniated species.

6. **Evaluating the Statements**:
We need to evaluate the following statements:
- The blue color is due to ammoniated electrons. **(True)**
- The solution is paramagnetic. **(True)**
- The blue color changes to brown on standing. **(Not True; it changes to bronze, not brown)**
- In a concentrated solution, the blue color changes to bronze and becomes diamagnetic. **(True)**

7. **Conclusion**:
The statement that is not true is the one that claims the blue color changes to brown on standing. The correct term is "bronze." Therefore, the answer to the question is that the third statement is incorrect.

### Final Answer:
The statement that is not true about the solutions of alkali metals in liquid ammonia is: "The blue color changes to brown on standing."

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