Because I need to solve symbolically a set of equation and it is not possible to use in the Maple Wrapper or in the Maxima plugin a varibale name with unicode characters; I mean use as variable name something like [SO₄^2- ] or the like, I need to define some conventions to represent these names, so:

- The square brackets are not considered

- Subscripts and Superscripts are added as simple numbers where required by their position

- Negative charge is displayed ad "m"(=minus) and the positive one with "p"(=plus)

- The quantity of charge is after the sign, if is 1 it is not displayed

 

So [SO₄^2- ] => SO4m2

 

To solve a problem of equilibrium in a solution we need always to proceed in a standard way using the following steps:

1-Write the equilibrium reactions that take place in the solution and define which are the chemical species involved

2-Write down an algebraic system of equations that allows the evaluation of the concentrations of all chemical species

involved to do this we need to write :

- one or more Equilibrium equation(s)

- one or more Materal balance equation(s)

- one Charge balance equation

 

Let's see how this apply analyzing what happens when we dissolve a Strong monoprotic acid HA in water at a concentration C_a, the reactions that take place are:

 

HA → H⁺ + A^-

H₂0 ⇄ H⁺ + OH^-

 

and the equations tha we can write are the following ones:

Equilibrium equation

Material balance on HA

Charge balance

but in equilibrium conditions a strong acid completely dissociates so its concentration is 0, i.e.

the solution of the equations system is:

and Eq2 simplifies

we discard the negative

solution L₂

a change of variables for plotting purposes , so we can compare directly the cologarithm of C_a with the pH of the solution.

for plotting have used Maxima Draw2D , there are some glitches in displaying the Y axis ( i.e the label pH )