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Kp cannot be used in place for Kc, but you can convert one into the other by using the formula: Kp= Kc(RT)^delta n. Delta n is equal to the moles of the products minus the moles of the reactants. This formula relates Kp to Kc, so you can convert one to the other.
Kc and Kp are different. Kc is defined by molar concentrations, whereas Kp is defined by the partial pressure of the gasses inside a closed system. However, you can convert between the two with the following equation: Kp = Kc(RT)^Δn.
Kp is for pressure, whereas Kc is for concentration. When writing out the formula for Kp, you must say the partial pressure of the compound (for example, P subscript O2). For Kc, you don't use the large P, you simply put it in brackets to indicate concentration.
IsabelLight2H wrote:If they just say "k" do we assume Kp? Because in one problem in the textbook they used K and then it was Kc.
I think you can assume Kp when both reactants and products are all in the gas phase, or if told to find the equilibrium constant in atm. But I think that it might be safe to simply assume that K just means Kc if not given any other specific information.
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