In a 500 ml flask, the degree of dissociation of PCl5 at equilibrium is 40% when the initial amount taken  is 5 moles. The value of equilibrium constant in moles/lit  for the decomposition of PCl5 is ( Given reaction, PCl5g⇌PCl3g+Cl2g )

Vvessel = 0.5 lit Degree of decomposition of PCl5 =.For every 1 mole PCl5 taken 0.4 moles decomposes.For every 5 moles PCl5 taken 'X' moles decomposes.Number of moles of PCl5 decomposed = 2For every 2 moles of PCl5 decomposing 2 moles each of PCl3 and Cl2 are formed.