Question

Why equitorial and axial bond lengths of PCl5 are not equal ?

Answer 1

in pcl5 the axial bonds suffer repulsion from the equatorial bonds so they become long and weak but in pf5 the axial and equatorial bonds are of nearly equal length because the repulsion between the bonds tries to make axial bonds longer but fluorine being most electronegative makes the P-F bond shorter as a result axial bonds become nearly equal to equatorial bonds

Answer 2

The axial bonds suffer more repulsion from the equatorial bond pairs therefore the axial bonds become slightly longer than the equatorial bonds.
Because of this the axial bond becomes weak thus, make PCl5 more reactive.