In a 0.100 m hf solution, the percent dissociation is determined to be 9.5%. calculate the ka for hf based on this data.

Answer : The dissociation constant (Ka) = 9.025 ×

Solution :  Given,

                Concentration HF solution = 0.100 M

                 % Dissociation = 9.5 %

The equation for dissociation of HF is :

The Ka expression for HF is :

       ............. (1)

Step 1 : we find the by using the concentration and % dissociation.

  = Concentration HF solution ×  % Dissociation

  = 0.100 M × = 9.5 × M

Step 2 : For , the concentration of   is equal to the  . From the above equation the stoichiometry of   and is 1:1.

Therefore,

=    = 0.100 M × =    =  9.5 × M

Now, put all the values in equation (1), we get

           = 9.025 ×