How can I calculate the dissociation of an acid?
The dissociation of a strong acid is easy, it will be nearly 100%.
Here is a video discussion of dissociation of strong acids and bases.
For a weak acid: To do this you'll need to use the Ka value of the acid and determine the equilibrium expression of the dissociation of that acid. Using the quadratic equation allows you to solve for the hydrogen ion concentration if you are given the initial concentration of the acid and the Ka value.
I'm including a video which discusses how to work with the dissociation of