Equilibria: compare question

Two separate gas-phase equilibria are set up in closed containers. In container 1, $\ce{PCl5(g) <=> PCl3(g) + Cl2(g)}$. In container 2, $\ce{N2O4(g) <=> 2NO2(g)}$. Both systems are allowed to reach dynamic equilibrium at the same temperature.

Compare the two equilibria in terms of:

(a) the expression for the equilibrium constant in terms of partial pressures, $K_p$, for each reaction, using the terms partial pressure and mole fraction;

(b) the effect on the position of equilibrium of an increase in pressure;

(c) the effect on the value of $K_p$ of adding a catalyst.