Like the poster above noted, the equilibrium constant for the concentration of species in gaseous equilibrium and their partial pressures may be the same value, but this often not the case. Partial pressure and concentration within a system are directly proportional
in value, meaning that while proportionally species have the same PP and concentration, their actual values may be multiple magnitudes larger or smaller.
For instance, take the hypothetical gaseous reaction
, at 200K in a 1.00 L reaction vessel. If there were 0.2 moles of A, 0.3 moles of B, and 0.5 moles of C at equilibrium, then 20% of the partial pressure in the system is due to A, 30% due to B, and 50% due to C. Likewise, the system is also 20% A, 30%B, and 50% C by concentration. However, this is not to state that concentration and PP are equal; using the ideal gas law will allow us translate concentration into PP and then find equilibrium concentration values.