Two oxides of nitrogen, `NO and NO_(2)` are allowed to react together at 243 K and form coloured compound of nitrogen (X), When compound (X) reacts with water to yeild another compound of nitrogen (Y). The shape of the anion (Y) molecule is

Options

A. angular
B. triangular planar
C. tetrahedron
D. square planar

Answer

To solve the problem step by step, we will analyze the reaction between the nitrogen oxides and the subsequent reactions to determine the shape of the anion (Y).

### Step 1: Identify the Reaction Between NO and NO2
We start with the two nitrogen oxides: nitric oxide (NO) and nitrogen dioxide (NO2). When these two gases react at a temperature of 243 K, they form a colored compound.

**Hint:** Think about the common reactions between nitrogen oxides and what products they might yield.

### Step 2: Determine the Product (X)
The reaction between NO and NO2 at the specified temperature produces dinitrogen trioxide (N2O3), which is the colored compound (X). N2O3 is known to be a blue-colored solid.

**Hint:** Recall the properties of nitrogen oxides and their typical products when combined.

### Step 3: Reaction of Compound X with Water
Next, we need to consider what happens when N2O3 reacts with water (H2O). The reaction of N2O3 with water yields nitrous acid (HNO2).

**Hint:** Consider the general behavior of nitrogen oxides when they react with water.

### Step 4: Identify the Compound (Y)
From the reaction of N2O3 with water, we obtain nitrous acid (HNO2). The relevant anion formed from nitrous acid is the nitrite ion (NO2^-).

**Hint:** Identify the anion that corresponds to the acid formed from the nitrogen oxides.

### Step 5: Determine the Shape of the Anion (Y)
The nitrite ion (NO2^-) has a specific molecular geometry. To determine its shape, we can analyze its Lewis structure. The nitrite ion has one nitrogen atom bonded to two oxygen atoms, with one of the oxygen atoms forming a double bond and the other forming a single bond. There is also one lone pair of electrons on the nitrogen atom.

**Hint:** Use VSEPR theory to predict the shape based on the number of bonding pairs and lone pairs.

### Step 6: Analyze the Geometry
The nitrite ion (NO2^-) has a total of three regions of electron density (two bonding pairs and one lone pair). According to VSEPR theory, this arrangement leads to a bent or angular shape.

**Hint:** Consider the hybridization and the resulting shape based on the number of bonds and lone pairs.

### Conclusion
The shape of the nitrite ion (Y) is bent or angular due to the presence of one lone pair of electrons on the nitrogen atom.

**Final Answer:** The shape of the anion (Y) molecule is angular.