How to compute the acid dissociation?

Question

are there given constant values?

Answer 1

See the following site to help you:

http://en.wikipedia.org/wiki/Acid_dissociation_constant

There are dissociation constants for amino acids, etc., but you can calculate using equation shown at above site.

Answer 2

By knowing concentration valves at equilibrium.These concentration values are determined experimentally using various methods.