Concept:A molecule is polar if it contains polar bonds that do not cancel each other out symmetrically.
Formula:$$ \mu \neq 0 \implies \text{Polar Molecule} $$
Solution:- Hydrogen Chloride (HCl) is a simple diatomic molecule.
- Chlorine (EN = 3.0) is much more electronegative than Hydrogen (EN = 2.1).
- This creates a permanent uneven sharing of electrons (a dipole), making the molecule polar. There are no other bonds to cancel this dipole out.
Why other options are incorrect:- Option A: \( \text{CCl}_4 \) is a perfectly symmetrical tetrahedron; dipoles cancel completely.
- Option B: \( \text{CO}_2 \) is perfectly linear; dipoles cancel perfectly.
- Option C: \( \text{AlCl}_3 \) is a perfectly symmetrical trigonal planar molecule; dipoles cancel.
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