Answer the following :
(a) `C Cl_(4)` is non-polar but `CH_(3)Cl` is polar.
(b) `SiF_(4)` is non-polar although Si-F bonds are polar.
(c ) A hetero-diatomic molecule is always polar.

Explanation

(a) Carbon tetrachloeide `(C Cl_(4))` is a symmetrical molecule with a regular tetrahedral geometry. Therefore, the polarises of the bonds cancel out and the molecule is non-polar. On the other hand, methyl chloride `(CH_(3)Cl)` has irregular geometery due to the presence of one C-Cl bond. The molecule has a specific polarity.
(b) Like `C Cl_(4)` the molecule `SiF_(4)` is highly symmetrical and has a tetrahedral geoometry. Therefore, bond polarities cancel out and it is non-polar in nature.
( c) A hetero-diatomic molecule (e.g. HF,HCl, ICl etc.) is dipolar on account of the electronegativity difference in the bonding atoms. However, the same may not be true for polyatomic molecules in which bond polarities may mutually cancel. For example, `BF_(3)` and `C Cl_(4)` molecules.