A0.100 m solution of the weak acid ha has a ph of 3.00. what is the ka for this acid?

The acid dissociation constant or Ka is a value used to measure the strength of a specific acid in solution. For a general dissociation of an acid solution,

HA = H+ + A-

we express Ka as follows:

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

Where the terms represents the concentrations of the acid and the ions. Assuming that the weak acid in the problem is HA, we first calculate for the concentration of H+ from the pH.

pH = - log [H+]
3.00 = - log [H+]
[H+] = 0.001 M

By the ICE table, we can calculate the equilibrium concentrations,
        HA      =      H+            +        A-
I      0.100           0                         0
C      -x               +x                      +x
 
E  0.1 - 0.001  0.001                  0.001

Ka = (0.001) (0.001) / .099
Ka = 1.0101x10^-5

the answer is b. dilution