Solve this:
Q. How many moles per litre of P C l 5 has to be taken to obtain 0.1 mol of C l 2 , if the value of equilibrium constant K c is 0.04?
(1) 0.15
(2) 0.25
(3) 0.35
(4) 0.05

Dear student,

The governing reaction for the above problem is
                    PCl5             PCl3 + Cl2    t=0         a                        0            0    t=t        a(1-α)             aα          aαwhere α is degree of dissociation, and a is moles of PCl5 per litre.aα = 0.1-----(1)Kc = PCl3Cl2PCl50.04 = aα.α1-α------(2)Putting value of aα from (1) in (2) and solvingα = 27Putting this value of α in (1),a=0.35.
Hence answer is (3).
Hope this helps,
Regards

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