pH at equivalence point

[leathersofa]

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okay TBR has gotten me pretty confused about how to find the pH at equivalence. They say how the pH at equivalence point can be found by doing pKa + 3 to find pH at equivalence if pKa is between 4 and 10. Note that this method is not affected by concentration factors.
They also have a second method where you can do pH = [pKa + pH(titrant)]/2

How do you differentiate between when to use the first method and when to use the second one because they both give different answers..?
And, even though TBR says (pKa + 3) is not affected by concentration factors, I feel like it is. A weak acid 1 M HA being titrated by a strong base cannot have the same equivalence point the same weak acid at 0.1 M.

Could someone please clear up the above for me? thank you!

 

[onedirection]

I'm pretty sure for at equilvalence point pH you'd have to use an ICE table/HH I guess, regardless I doubt the MCAT will make you go through an ICE table calculation

just know SA + SB Eq pt pH = 7
If it's a strong base weak acid > 7
And SA + WB < 7

 

[leathersofa]

haha okay, thats fine. thank you, that just simplifies it much better!