Equations for the total amounts of substances of the particles A, B, and Cu are as follows:
a = n(A−) + n(HA) + n(CuA)
b = n(B−) + n(HB) + n(CuB)
m = n(Cu+) + n(CuA) + n(CuB)
The amounts of precipitates are eliminated from the equations:
a + b− m = n(A−) + n(HA) + n(B−) + n(HB)− n(Cu+ ) = 0
because, when forming a system of both solid salts, the total number of particles A and B (a + b) must be equal to the total number of cations Cu+, i. e. to the value of m. When the amounts of substances are divided by the volume of the solution, we get concentrations, and thus: