the reaction contains initially 5 moles of CO and 2 moles of H2O.the volume is 1 litre.but at equilibrium it is 0.5 moles of h2o .then value of Kc for reaction is.
Interesting but you gave no equation. Here is what I suspect.
.........CO + H2O ==> CO2 + H2
I........5.....2.......0.....0
C........-x...-x.......x.....x
E.......5-x...2-x......x.....x
The problem tells you that 2-x = 0.5. Evaluate the terms, substitute into Kc expression and evaluate kc.