What is the Ka of trichloroacetic acid?

Question

Trichloroacetic acid is a corrosive acid that is used to precipitate proteins. The pH of a 0.050 M solution of trichloroacetic acid is the same as the pH of a 0.040M HClO4 solution. Calculate Ka of trichloroacetic acid.
Please help me in solving the problem related to acids and bases . Thanx in advance...

Answer 1

HClO4 is a strong acid. Thus it dissociated completely and since it is monoprotic it will give [H+]=0.040

The solution of trichloroacetic acid has the same pH as that of HClO4, thus it has the same [H+]

.. .. .. .. .. CCl3COOH <=> CCl3COO- + H+
Initial .. .. .. .. 0.05
Dissociate .. .. x
Produce .. .. .. .. .. .. .. .. .. .. .. .. x .. .. .. .. ..x
At Equil. .. 0.05-x .. .. .. .. .. .. .. ..x .. .. .. .. .x

Ka= [CCl3COO-][H+] / [CCl3COOH] = x^2/(0.05-x)

but x=[H+]=0.04

Thus Ka= (0.04^2)/(0.05-0.04) = 0.16

Answer 2

15. Trichloroacetic acid (CCl3CO2H) is a corrosive acid that is used to precipitate proteins. The pH of a 0.050 M solution of trichloroacetic acid is 1.4. Calculate Ka.

Answer: Ka = 0.155

Ya know, I googled "Ka" and "trichloroacetic acid" and lookie what I found.... Isn't it odd that it's word for word?

Answer 3

you can use a data site to find out the constants like Ka, in the general case

Ka = [H+][OH-]/[HA]