Solved: CHEMISTRY Question for NEET

NEET CHEMISTRYMedium

A molecule among the following that has the maximum dipole moment is:

CO₂

CH₄

NH₃

NF₃

$CO_2$ : Linear structure ( $O=C=O$ ). The bond dipoles of the two $C=O$ bonds are equal and opposite, cancelling each other out. Resultant $\mu = 0$ .
$CH_4$ : Tetrahedral structure. The vector sum of the four $C-H$ bond dipoles is zero due to symmetry. Resultant $\mu = 0$ .

Both molecules have a pyramidal shape with one lone pair on the Nitrogen atom.
In $NH_3$ : Nitrogen is more electronegative than Hydrogen. The bond moments point towards Nitrogen. The orbital dipole due to the lone pair is in the same direction as the resultant bond moment of the three $N-H$ bonds. These effects reinforce each other, resulting in a high dipole moment ( $\approx 1.47 D$ ).
In $NF_3$ : Fluorine is more electronegative than Nitrogen. The bond moments point towards Fluorine (away from Nitrogen). The orbital dipole of the lone pair points in the opposite direction to the resultant bond moment of the three $N-F$ bonds. These effects partially cancel each other, resulting in a low dipole moment ( $\approx 0.23 D$ ).

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