Answer:
Moles of gas between reactants and products
Explanation:
Both Kc and Kp are equilibrium constants of chemical reactions at equilibrium. While Kc stands for the general equilibrium constant in terms of concentration of both reactants and products, Kp stands for the equilibrium constant in terms of pressure.
Hence, while we are writing the equilibrium constant equation in terms of pressure, we only consider the reactants and products that are gaseous in nature only. We do not consider other reactants and products as we have done when writing for Kc.
Hence, when converting between these units, we should consider the moles of substances which are gaseous on both the reactant and product side
