[Big-Daddy]

Equivalence for a mixture is when you add enough titrant for all reactions to complete. But then titration percentage doesn't make much sense, as it would be function of the solution composition, which you don't know beforehand.

Not that it matters much - knowing composition you should be able to find out which substance will he the last one titrated and it should help you find out parameters of the end point. But I refuse to discuss details, as you will get lost pretty soon and we will waste time. You are looking for the most generalized approaches without understanding how to deal with simple problems, which just makes you more and more confused.

But this is a problem I need to overcome. So let's take it step by step then.

Titration of HA (weak acid) with BOH (weak base): When C_HA*V_HA=C_BOH*V_BOH we have reached equivalence point.
Titration of H_nA with BOH: First equivalence point is at C_HA*V_HA=n*C_BOH*V_BOH. Second is at C_HA*V_HA=(n-1)*C_BOH*V_BOH. nth equivalence point is at C_HA*V_HA=C_BOH*V_BOH. Is this right, or how can I make it right?

Also, if I had a ([H⁺],V_titrant) graph ([H⁺] on x-axis, V_titrant on y-axis), i.e. inverted axes of a titration curve, could I take d/d[H⁺] of V_titrant as a function of [H⁺] and the constants, set to 0 and all real positive solutions would be equivalence points? After all the real definition is the point at which rate of change of pH is highest right?