Question

Which of the following molecules is correctly paired with its molecular polarity?
F
H20 : non-polar
G
CH4 : polar
H
CO2 : polar
NH3 : polar

Answer 1

Answer:

The correctly matched pair is :

$NH_{3}$ is Polar

Explanation:

Polarity is decided by net dipole moment . If a molecule has 0 dipole moment then it is non-polar .

If a molecule has some value of dipole moment then it is polar.Unit of dipole moment is Debye(D)

${dipole moment = charge \times distance}$

In chemical value of dipole is based on two factors :

1. There should be heteroatomic bond in a given compound..e.g H-Cl , C-N

(not C-C, N-N)

2. The molecule should be unsymmetrical in shape.

note : even if all bonds are heteroatomic but shape is symmetrical , then also dipole moment can be zero

CORRECT MATCHES

$H_{2}O$ : Polar

It has net dipole moment of 1.85 D because its shape is bent (unsymmetrical) and all bonds are heteroatomic.

$CH_{4}$ :Non-Polar

All bonds are heteroatomic(C-H) but shape is symmetrical(tetrahedral), so net dipole is zero

$CO_{2}$ : Non -Polar

All bonds are heteroatomic(C=O) but shape is symmetrical(linear), so net dipole is zero