clarification on titration equations TBR

[echoyjeff222]

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For calculating the equivalence point, TBR gives a shortcut equation with the pKa (acid) + pH (base) / 2 to get the pH of the equivalence point. However, it also says in the very beginning of the chapter that the equivalence point is found by looking at the conjugate base (if we're titrating a weak acid to start) and using the other shortcut equation with pOH = 1/2pKb - 1/2log[A-] ... which one should I use? I understand the second one is probably more "correct" but on the test, can I just use the first one? Thanks!

 

[pepocho]

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[echoyjeff222]

But at the equivalence point specifically, I would only have the conjugate anion, which I could apply the second equation to, couldn't I?

 

[pepocho]

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