Choose the correct statement.

Options

A. Polar molecules have permanent electric dipole moment.
B. `CO_(2)` molecule is a polar molecule.
C. `H_(2)O` is non-polar molecule.
D. The dipole field at large distances falls of as `(1)/(r^(2)).`

Explanation

To solve the question, we need to analyze the statements provided and determine which one is correct. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Analyze the first statement
The first statement claims that polar molecules have a permanent electrical dipole moment.
- **Explanation**: Polar molecules do indeed have a permanent dipole moment due to the uneven distribution of electron density. This means that they have a positive end and a negative end. Therefore, this statement is **correct**.

### Step 2: Analyze the second statement about CO2
The second statement discusses CO2 (carbon dioxide) and whether it is a polar molecule.
- **Explanation**: CO2 is a linear molecule with two oxygen atoms symmetrically placed around a carbon atom. The dipoles from the C=O bonds cancel each other out, making CO2 a **non-polar molecule**. Thus, this statement is **incorrect**.

### Step 3: Analyze the third statement about H2O
The third statement discusses H2O (water) and whether it is a polar molecule.
- **Explanation**: H2O has a bent molecular geometry, and the oxygen atom is more electronegative than hydrogen, leading to a net dipole moment. Therefore, H2O is indeed a **polar molecule**. This statement is **correct**.

### Step 4: Analyze the statement about dipole field
The fourth statement claims that the dipole field at a large distance falls off as \( \frac{1}{r^2} \).
- **Explanation**: The electric field due to a dipole actually falls off as \( \frac{1}{r^3} \) at large distances, not \( \frac{1}{r^2} \). Therefore, this statement is **incorrect**.

### Conclusion
Based on the analysis:
- The first statement is **correct**.
- The second statement about CO2 is **incorrect**.
- The third statement about H2O is **correct**.
- The fourth statement about the dipole field is **incorrect**.

Thus, the correct statement is that polar molecules have a permanent electrical dipole moment.

### Final Answer:
The correct statement is: **Polar molecules have a permanent electrical dipole moment.**