Question

The initial concentration of a weak acid HZ is 0.100 M. The pH of the solution (after dissociation) is 1.70. What is the acid's % dissociation?

Answer 1

A weak acid is an acid that dissociates incompletely, releasing only some of its hydrogen atoms into the solution.

Here's the equation for the dissociation:

If the acid had dissociated completely, you would have had a 100% dissociation (look out! you should never get a value of [H⁺] higher than the inicial concentration of the acid), but this is a weak acid, so only a part dissociates, that means, only a fraccion transforms into products (H⁺ and Z^-).

Where [H⁺] is how much acid has dissociated and [HZ]_iis how much acid you had in the beggining.

The acid's % dissociation is 20%