The pH at one half the equivalence point in an acid-base titration was found to be 4.32. What is the value of?

The pH at one half the equivalence point in an acid-base titration was found to be 4.32. What is the value of Ka for this unknown acid? This is the only one I have been having trouble with... can someone help me get the correct answer please?|||Using the Hendersen/Haselbach equation


pH = Ka + log [base]/[acid] note that when the concentration of the base and acid forms are equal the log of this ratio ( the ratio is 1 ) is 0.


So at the point where the acid form and the base form are equal the pH = pKa. When you are titrating an acid with a base..you are generating the conjugate base of that acid so when you are 1/2 through the reaction ..you will have converted 1/2 the acid to an equal amount of its conjugate base sooo [acid] = [base] so pH = pKa





since the pH = 4.32 then the pKa = 4.32 so the ionization constant is


4.8 X 10^-5





check





-log 4.8 x 10^-5 = 5 - log 4.8 = 5- 0.68 = 4.32