Which of the following statements regarding `N_(2)O_(4)` is not correct?

Options

A. It is a planar molecule
B. It is used as non-aqueous solvent
C. It involves N-N bond which is Shorter than that N-N bond in hydrazine
D. Ammonium nitrate in `N_(2)O_(4)` acts as a base

Answer

To determine which statement regarding \( N_2O_4 \) (dinitrogen tetroxide) is not correct, we will analyze each statement one by one.

### Step 1: Analyze the first statement
**Statement 1:** "It is a planar molecule."

- **Analysis:** \( N_2O_4 \) is indeed a planar molecule. It is the dimer of \( NO_2 \), and its structure consists of two nitrogen atoms bonded together with double bonds to oxygen atoms. The hybridization of nitrogen in \( N_2O_4 \) is \( sp^2 \), which results in a planar structure. Therefore, this statement is **correct**.

### Step 2: Analyze the second statement
**Statement 2:** "It is used as a non-aqueous solvent."

- **Analysis:** \( N_2O_4 \) is known to be a self-ionizing aprotic solvent and can be used as a non-aqueous solvent. This statement is also **correct**.

### Step 3: Analyze the third statement
**Statement 3:** "It involves an N-N bond which is shorter than the N-N bond in hydrazine."

- **Analysis:** The N-N bond length in \( N_2O_4 \) is approximately 1.78 Å, while in hydrazine (\( N_2H_4 \)), the N-N bond length is about 1.45 Å. Therefore, the N-N bond in \( N_2O_4 \) is actually longer than that in hydrazine. This statement is **incorrect**.

### Step 4: Analyze the fourth statement
**Statement 4:** "Ammonium nitrate in \( N_2O_4 \) acts as a base."

- **Analysis:** In the context of \( N_2O_4 \), when it undergoes ionization, it produces nitrosyl and nitrate ions. The nitrosyl salt can act as an acid, while metal nitrates can behave as bases. Thus, this statement is **correct**.

### Conclusion
The statement that is not correct regarding \( N_2O_4 \) is the third one: "It involves an N-N bond which is shorter than the N-N bond in hydrazine."