Pseudo Reaction

[Mahir_Hasan2C]

Why is it that you are allowed to exclude one of the species when finding the order of that species?

[Sam Joslyn 1G]

I'm not entirely sure if this answers your question, but a pseudo-first-order reaction is when you saturate the reaction with an excess of all the products but one, effectively making the change in concentrations of the saturated reactants negligible so that the rate is only dependent on the reactant with a normal concentration. That is why you can not include the reactants in excess-- their rate of change is negligible.