Question

how we choose more polar compound

Answer 1

Hello,
You must know Fajan's rule.
It's about Polarizibility and polarizing power.

The compound which has more electronegativity difference, {i.e. if there is a compound AB and if B has the largest electronegativity so then B - A > 1.7 or 1.9. Some books tell that the difference must be greater than 1.7 (better take this value)
and some other books tell the difference must be greater than 1.9.} these types of compounds are called a polar compound.
Example: NaCl.
Electronegativity of Na = 0.93
Electronegativity of Cl =3.16
Difference = 3.16 - 0.93 = 2.23
Therefore this compound is polar.
Even Water (H2O)
Like dissolves in like so polar dissolves in polar.
That is why NaCl dissolves in H2O.

And if the compound has the difference of electronegativities less than 1.7, then this type of compounds are said to be non-polar compounds.
Example: CO2 (Carbon Dioxide)
Electronegativity of C = 2.55
Electronegativity of O = 3.44
Difference = 3.44 - 2.55 = 0.89
Therefore this compound is non-polar.
Even Benzene (C6H6), Carbon Tetra-Chloride (CCl4)
Unlike dissolves in unlike so non-polar dissolves in non-polar.
That is why CO2 does not dissolves in H2O but dissolves in CCl4 and C6H6

Hope my answer helps you