For reactions involving gases, an increase in pressure is no different from increasing the concentration of reactant particles, thus increasing the rate of reaction. But for reactions involves different phases, such as both solid and liquid, what will the pressure increase cause? Will it increase the rate of reaction? Or, because the rate also depends on other reactants and in reactions involving different phases, will pressure not change significantly even if gas is present?
There is probably going to be a separate reaction rate law for each phase, assuming that the reaction even occurs in other phases. Of course, in liquid and solid phases, the pressure is going to have much less of an effect than in a gas phase. Another consideration is that there may be interphase mass transport between the various phases (at their interfaces), and this may have to be taken into account in the chemical species mass balances for the individual phases.