Among the following, the non-polar molecule is                        

BCl₃

Explanation:

Despite having polar B-Cl bonds, BCl₃ is a non-polar molecule due to its trigonal planar shape.

• Bond Polarity: BCl₃ contains polar B-Cl bonds, as chlorine is more electronegative than boron. This creates dipole moments in each bond.
• Molecular Geometry: The geometry of BCl₃ is trigonal planar. The three B-Cl bonds are arranged symmetrically around the central boron atom.
• Dipole Moment Cancellation: Due to the symmetrical arrangement of the bonds, the individual dipole moments of the B-Cl bonds cancel each other out. This results in no net dipole moment in the molecule.
• Conclusion: Since the dipole moments cancel each other, BCl₃ is a non-polar molecule, even though it has polar bonds.

Concept Behind Polarity:

• Molecular polarity depends on both the individual bond polarities and the shape of the molecule.
• If the molecular geometry is symmetrical, the dipole moments can cancel each other, making the molecule non-polar, even if it contains polar bonds.
• In contrast, molecules like NCl₃, KF, and H₂O have asymmetrical shapes or lone pairs that prevent the cancellation of dipole moments, leading to a net dipole moment and making them polar.