in the reactn-> CaCO3(s)---->CaO(s)+CO2(g) , we can evaluate both Kp & Kc and since delta n not=0, so also Kp not=Kc. so, in delta G= - RT lnK , what should we put in place of K (Kp or Kc)? Plz explain details when to use what.

Dear Padma Bhushan,

K involves all species like pure solids, pure liq., gas solutions

Kc is used for species whose concentration is variable like gases n solutins and it is not used for pure components like pure solid,

pure liquid and solvents.

Kp exists when no component of the equilibrium is in solution state and at least one gaseous react./product is present.

Kc has units of conc. and Kp has that of pressure so u can find the unit and then say K as kc or Kp.

Please feel free to ask your queries here. We are all IITians and here to help you in your IIT JEE preparation.

All the best.

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