What are Oil in water emulsions ? explain with examples.

Oil in water emulsions: In this type of emulsions, oil acts as (organic solvent) dispersed phase and water acts as dispersion medium. Some examples of this type of emulsions are milk, vanishing cream, etc. In milk, liquid fat is dispersed in water.

How many 3c-2e bonds and 3c-4e are there in Al2(CH3) 6?

Al2(CH3)6 is dimer of Al(CH3)3 , which is dimerized by formation of bridge bond namely 3C - 2e bond (banana bond ) as well as 3C - 4e bond .

Why are all P-Cl bond lengths equal in PCl3 but different in PCl5?

Phosphorus atom of PCl3, is sp3 hybridised. so orbital involved in hybridization are s and p only and PCl3 has a trigonal pyramid structure.

However in case of PCl5, the hybridisation is sp3d. (sp3d, the hybridisation can represent as also sp2+pd) and it acquired TBP ( trigonal pyramidal structure).
We know that in TBP, there is two type of bond present I.e. axial (longitudinal) and equatorial bond. Bond length of axial bond is longer (coordinate bond ) while equatorial bond is shorter due to covalent nature ( formed by overlapping of atomic orbitals).