[hjjou]

Hi,
I would like to know what euation I should use when I am try to calculating the pH of a binary acid soultion (e.g. a mixture solution with acetic and lactic).  For a simple acid solution, I can use the equation pH=pKa+log[A-]/[HA], what I don't quite clear is how can I calculate the pH or concentration of a more complicated solution like binary acids system with known pkas for the acids.  Thanks for any input.

[Donaldson Tan]

Simultaneous Equations.

[hjjou]

To Geodome:

Thanks for replying.  What are Simultaneous Equations?  I am not a Chemistry student, this is work related.  Can you explain a little more or refer me to any literature?  Thanks.

[AWK]

For weak acid solution
pH= -log(SQRT(Ka x c))
For mixture of a few weak acids
pH=-log(SQRT(K₁ x c₁ + K₂ x c₂ + ...))

Your equation is used for buffer solutions.

[hjjou]

To AWK:

Thanks so much.

So I used the wrong equation?

Is there a textbook or literature I can read?

[AWK]

Your eqaution is true but useless for pH calculation of weak acid because it contains two unknown variables.

read on weak acids in university textbooks on general or physical chemistry