To make the second term positive, by convention the ratio is written with the more negative species above. Write out the definition of the dissociatio
To make the second term positive, by convention the ratio is written with the more negative species above. Write out the definition of the dissociation constant. Solve for hydrogen ion concentration and take the logarithm of both sides. When acid concentration equals conjugate base concentration at the half-equivalence point, it reduces to pH is equal to pKa. This is, FTP, what equation stating that the pH of a buffer is equal to the pKa plus the logarithm of base over acid concentrations?
To make the second term positive, by convention the ratio is written with the more negative species above.
Henderson-Hasselbalch equation (note that it is -balch, not -bach)