# Strong or weak acid?

## Homework Statement

How can you determine if an acid is strong or weak given the titration curve? I need two reasons.

## The Attempt at a Solution

1 Reason that it is weak is that its being titrated by a strong base and the equivalence point is above pH of 7.

Need a 2nd

Last edited:

Borek
Mentor
Take two titration curves and compare them.

You may try (there is a free trial).

Not sure what the acid is, but through a tritaion calculation I found the concentration of the acid to be 0.2083M.

That may not be correct..

Heres the data:
NaOH: 0.125M
25mL
acid: 15mL
unknown concentration

But it is a monoprotic acid

symbolipoint
Homework Helper
Gold Member
Depending on concentrations used, pH will change at a very high rate through pH 7 through the equivalence point. A weak acid will further show fairly small change in pH as the titrant is added over a "long" range of titrant addition until close to the equivalence point. Equivalence point should happen at about pH 8 or greater for a weak acid.

Yes, it happens at pH = 8.7

It just occured to me that weak acids do not 100% dissociate

So could I use the pH of 8.7 to determine the concentration of H+ and compare that number to the concentration of the acid, and if they are different, that means it wasnt 100% dissociated?

HX ---------> H+ + X-
0.2M -------> 2x10^-9M

[H+] = 10^-pH = 2x10^-9

Borek
Mentor
At equivalence point there is (almost) no acid, there is (almost) only its salt.

Well whats another way I could show that this acid is weak?

symbolipoint
Homework Helper