When are Kp and Kc equal for this reaction?

Question

Under which circumstances are Kp and Kc equal for the reaction aA(g)+bB(g)⇌cC(g) ?

Answer 1

The equation for converting between Kp and Kc is ...

Kp = Kc (RT)^∆n

Thus, the only way that Kp and Kc can be equal is when ∆n = 0. This then reduces the equation to

Kp = Kc(RT)⁰ = Kc x 1 = Kc

So, in the current problem, the circumstances when Kp = Kc would be when the sum of a and b = c

or ... ∑a + b = c