Which of the following statements is not ture about the dilute solutions of alkali metals in liquid ammonia ?

Options

A. They are deep blue coloured solutions.
B. They are highly conducting in nature.
C. They are diamagnetic in nature.
D. Ammoniated cation and solvated electron are formed in the solution.

Explanation

To determine which statement is not true about the dilute solutions of alkali metals in liquid ammonia, we will analyze the properties of these solutions step by step.

### Step 1: Understand the Reaction
When alkali metals (denoted as M) are dissolved in liquid ammonia, they react to form ammoniated metal cations and solvated electrons. The general reaction can be represented as:
\[ M + n \text{NH}_3 \rightarrow [M(\text{NH}_3)_n]^+ + e^- \]
Here, \( [M(\text{NH}_3)_n]^+ \) is the ammoniated cation, and \( e^- \) represents the solvated electron.

**Hint:** Remember that the reaction involves the formation of cations and solvated electrons.

### Step 2: Identify the Color of the Solution
The presence of solvated electrons gives the solution a characteristic deep blue color. This is a well-known property of dilute solutions of alkali metals in liquid ammonia.

**Hint:** Consider the visual properties of the solution when solvated electrons are present.

### Step 3: Conductivity of the Solution
The dilute solutions of alkali metals in ammonia are known to be highly conducting. This is due to the presence of free-moving charged particles (the ammoniated cations and solvated electrons) that can carry electric current.

**Hint:** Think about how the presence of charged particles affects the ability to conduct electricity.

### Step 4: Magnetic Properties
Next, we need to examine the magnetic properties of the solution. Alkali metals in dilute ammonia solutions are actually paramagnetic due to the presence of unpaired electrons in the solvated electrons. Therefore, they are not diamagnetic.

**Hint:** Recall the difference between paramagnetic and diamagnetic substances based on electron configuration.

### Step 5: Formation of Ammoniated Cations and Solvated Electrons
It is also true that both ammoniated cations and solvated electrons are formed in the solution, as indicated by the reaction we discussed earlier.

**Hint:** Make sure to verify the formation of products in the reaction.

### Conclusion
After analyzing the statements:
1. They are deep blue colored solutions - **True**
2. They are highly conducting in nature - **True**
3. They are diamagnetic in nature - **Not True**
4. Ammoniated cation and solvated electron are formed in solution - **True**

The statement that is not true is the third one: "They are diamagnetic in nature."

**Final Answer:** The statement that is not true about the dilute solutions of alkali metals in liquid ammonia is that they are diamagnetic in nature.