Posted: Fri Dec 04, 2015 8:15 pm
Is there anyway to know when to use Henderson-Hasselbalch and when to use ICE box, or are they always interchangeable?
Posted: Fri Dec 04, 2015 8:28 pm
You use the HH equation when the reaction involves a weak acid and its conjugate base. Usually this implies that the Ka value is going to be smaller than 1 x 10-4. However if the Ka value is larger than that value then it is safer to go with the ICE box.
Essentially, the HH equation is an approximation. This is why reactions with very small equilibrium constants allow us to utilize this equation. However, when the equilibrium constant isn't small enough, then we have to use the ICE box.