Which among the following is a correct decreasing order of thermodynamic stability of the complexes?

Identify the process from following such that volume of system remains constant.

Identify the instrument used to find crystal structure from following :

In a solution, mole fraction of solute is 0.2 , when lowering in vapour pressure is 10 mm Hg . To get lowering of vapour pressure of 20 mm Hg , mole fraction of solute in solution is