What is the relationship between the equilibrium constant in terms of concentration \(K_c\) and the equilibrium constant in terms of partial pressure \(K_p\)?

For an ideal gas,

Substitute eq1 in the general equilibrium constant expression in terms of concentration,

Substitute the general equilibrium constant expression in terms of partial pressures, *K _{p}*, in eq2

where *Δn* = *sum of stoichiometric coefficients of products* – *sum of stoichiometric coefficients of reactants*.

Note that *K _{p }*=

*K*if

_{c}*Δn*= 0.