How do you predict the pH of a buffer solution using the Henderson-hasselbalch equation?

1 Answer
Jan 18, 2017

Answer:

It should be fairly close to the #pK_a# of the weak acid used in the buffer.

Explanation:

See this old answer. For the weak acid #HA# mixed with appreciable quantities of its conjugate base:

#pH=pK_a+log_10{([A^-])/([HA])}#

Clearly, when #[A^-]=[HA]#, then #pH=pK_a#. Why so? The #pH# at the point of half-equivalence is therefore used to measure #pK_a#.