Which of the following are arranged in the decreasing order of dipole moment ?

Options

A. `CH_(3)Cl, CH_(3) Br, CH_(3) F`
B. `CH_(3)Cl, CH_(3)F, CH_(3) Br`
C. `CH_(3) Br, CH_(3) Cl, CH_(3) F`
D. `CH_(3) Br, CH_(3) F, CH_(3) Cl`

Explanation

To determine the decreasing order of dipole moments for the compounds CH3F, CH3Cl, and CH3Br, we need to consider the electronegativity of the halogen atoms involved and how they influence the dipole moment.

### Step-by-Step Solution:

1. **Understanding Dipole Moment**:
The dipole moment (μ) is a measure of the separation of positive and negative charges in a molecule. It depends on the difference in electronegativity between the atoms involved. The greater the difference in electronegativity, the larger the dipole moment.

2. **Identify the Compounds**:
The compounds we are comparing are CH3F (methyl fluoride), CH3Cl (methyl chloride), and CH3Br (methyl bromide).

3. **Electronegativity Values**:
- Fluorine (F) has the highest electronegativity (around 4.0).
- Chlorine (Cl) has a lower electronegativity (around 3.0).
- Bromine (Br) has an even lower electronegativity (around 2.8).

4. **Direction of Dipole Moment**:
In each compound, the dipole moment will point from the carbon atom (C) towards the halogen atom (F, Cl, or Br) because the halogen is more electronegative than carbon. The hydrogen atoms (H) are less electronegative than carbon and do not significantly affect the dipole moment in this case.

5. **Comparing Dipole Moments**:
- For CH3F, the dipole moment is influenced by the high electronegativity of fluorine, resulting in a strong dipole moment.
- For CH3Cl, chlorine is less electronegative than fluorine, leading to a smaller dipole moment than CH3F.
- For CH3Br, bromine is the least electronegative among the three halogens, resulting in the smallest dipole moment.

6. **Arranging in Decreasing Order**:
Based on the electronegativity values and the resulting dipole moments, we can arrange the compounds in decreasing order of dipole moment:
- CH3F > CH3Cl > CH3Br

7. **Conclusion**:
Therefore, the correct order of dipole moments from highest to lowest is CH3F > CH3Cl > CH3Br.

### Final Answer:
The decreasing order of dipole moment is: **CH3F > CH3Cl > CH3Br**.