SUPPOSE 1 mole of A and B each TAKEN then 0.8 mole/litre of C and D each formed remaining CONCENTRATION of A and B will be (1 ? 0.8) = 0.2 mole/litre each. \[Kc=\frac{[C]\,\,[D]}{[A]\,\,[B]}=\frac{0.8\times 0.8}{0.2\times 0.2}=16.0\]