Question

Why are all P-Cl bond lengths not equal in PCL5?

Answer 1

i suggest you to read VSEPR theory and i believe that after you read it you will be clear on this and similar questions...

Answer 2

There are two bonds in PCl5 .One is Equatorial and other
is Axial, because of the repulsion factor one is longer
and the other shorter.
The bond nature is trigonal bipyramid. Two axial bonds of
same length are at angle 90. Three equatorial bonds of same
length are at bond angle of 120.
This is due to the minimum repulsion of charge between
the Cl atoms