Solution:
x 0 0 initially
(x -a) a a at equilibrium
But [Cl2 ] = 0.1 mol L-1
So [PCl3] = 0.1 mol L-1
and
and Kc = 0.0414
Since
0.0414x-0.00414 = 0.01
0.0414 x= 0.01414
x =5 moles