Acids and Bases (2 of 2)
Part 1 of Acids and Bases is located here.
At equilibrium, the rate of dissociation of the product
AB is equal to the rate of associate of the reactant
∴ at equilibrium:
Kd = [A] [B] / [AB]
Which is derived from an example such as:
AB ↔ A + B @ Equilibrium
pH indicators work because of the dissociation of the H+ ions in the indicator itself.
|Phenolphthalein||8 – 10|
|Methyl Red||4.5 – 6|
|Bromothymol||6 – 7.6|
Buffer solutions resist changes in pH.
The buffer solution absorbs the proton
HA + H2O ↔ H3O+ + A–
Ka = [H3O+] [A–] / [HA]
-log(Ka) = -log([H3O+] ([A–] / [HA]))
-log(Ka) = -log([H3O+]) – log([A–] / [HA])
pKa = pH – log([A–] / [HA])
pH = pKa + log([A–] / [HA])