A given volume of a buffer solution contains #6.85 x 10^-3# mol of the weak acid HY and #2.98 x 10^-3# mol of the salt NaY. The pH of the buffer solution is 3.78. How do you calculate the value of #pKa# for the acid HY at this temperature?
Well, the buffer equation holds that....
...we finally get
Now we were quoted molar quantities of the acid and its conjugate base....NOT concentrations...but given we have the quotient...
And so we solve for