ICE Tables vs. Henderson-Hasselbach

[Cain]

I know that in lecture you stated that we could use the ICE tables or the Henderson-Haselbach; My question is what are the parameters that we use to determine when to use one or the other? Could we use the 5% rule here, or is it a variation of that rule? Thank you in advance for your time.

[Paul Tate]

HH equation will work if the 5% rule is valid AND that the acid and base concentrations are 100-1000 times greater than the Ka.

That second part is directly out of the book, but what I taught in class is that the ration of base/acid should be within 100 times of each other. These are saying two different things, however, in application they get to almost the same conclusion. The bottom line is that it is usually VERY clear when the HH equation can be used, when the is a problem where both HA and A- minus are given then you can count on it being an HH problem otherwise they would just give you the initial conc. of HA OR A-.

Paul