K and Q calculations

[Khachik_Hmayakyan_2E]

In some questions it Is asked to write the reaction quotient Q or the equilibrium expression K. The answers for these seem to switch between calculating with the partial pressure P[product]/P[reactant] and calculating with Kc instead without the notation for partial pressure being involved in the equation. How should we know when to include P and when to only use concentrations in our calculations?

[Reem Abu-Shamma 2H]

Kc and Kp are both gas equilibrium constants. Which one you need to find depends on what is given in the question. If the concentration of the reactants and products is given then you find Kc. If partial pressure is given then you find Kp.