The correct decreasing order of dipole moment in CH3CI, CH3Br and CH3F is (A) CH3F > CH3CI > CH3Br (B) CH3F > CH3Br > CH3CI (C) CH3CI> CH3F > CH3Br (D) CH3CI> CH3Br > CH3F

To determine the correct decreasing order of dipole moments in CH3Cl, CH3Br, and CH3F, we need to consider the electronegativity of the halogens involved and how it affects the dipole moment of each molecule. The dipole moment is a vector quantity that depends on both the charge separation and the distance between the charges. In these molecules, the carbon atom is bonded to a halogen atom, which creates a polar bond due to the difference in electronegativity between carbon and the halogen.

Electronegativity and Dipole Moments

Electronegativity is a measure of an atom's ability to attract and hold onto electrons. In our case, the halogens have the following electronegativities:

• Fluorine (F): 4.0
• Chlorine (Cl): 3.0
• Bromine (Br): 2.8

From this, we can see that fluorine is the most electronegative, followed by chlorine, and then bromine. This means that the C-F bond will have the highest polarity, followed by C-Cl, and then C-Br.

Analyzing Each Compound

Now, let’s analyze the dipole moments of each compound:

• CH3F: The C-F bond is highly polar due to fluorine's high electronegativity. This results in a significant dipole moment.
• CH3Cl: The C-Cl bond is less polar than C-F but more polar than C-Br, leading to a moderate dipole moment.
• CH3Br: The C-Br bond is the least polar among the three, resulting in the smallest dipole moment.

Comparing Dipole Moments

Given the polarities of the bonds, we can conclude that the dipole moments will follow this order:

• CH3F has the highest dipole moment.
• CH3Cl has a moderate dipole moment.
• CH3Br has the lowest dipole moment.

Final Order

Thus, the correct decreasing order of dipole moments is:

CH3F > CH3Cl > CH3Br

Looking at the options provided, the correct answer is (A) CH3F > CH3Cl > CH3Br.