5B: Polyprotic Acids And Buffers Flashcards
How do polyprotic acids ionize
In steps, with Ka values for each step
What happens to the values of Ka after each ionization? Do 2nd and third ionizations affect pH?
Ka1>Ka2>Ka3. The second and third ionization does not affect the pH, except for sulfuric acid
What does the second ionization step determine
Determines the doubly ionized anion concentration
When do acids behave unusually such as protonated nitric acid
When they are concentration. It can produce No2+ which is a potent nitrating agent and flammable
What is the result of the presence of a common ion? What is the common ion effect
The presence of a common ion supresses the ionization of the acid due to Le Chatliers principle. The common ion effect is the shift in equilibrium caused by the addition of a compound having an ion in common with the dissolved substance.
When the common ion effect is in place, how do you determine the pH?
PH=pKA+log([c. Base]/[acid])
If a solution is a buffer solution, their pH do not change drastically with:
Dilutions, additions of an acid or base
Explain the acid-base equilibrium between an acid or conjugate base if you add more H30+ or OH-
Eq. Shifts slightly to the left if you add more H3O+
Eq. Shifts slightly to the right if you add more OH-
If you have a buffer solution, when a strong acid/base is added, what happens?
The strong acid/base is replaced with a weak acid/base
What is considered a simple buffer solution.Why can the buffer absorb both OH- and H+
A weak monoprotic acid and a salt of its conjugate base. It can absorb both because both acid and conjugate base are present in comparable amounts
More generally, buffer solutions can be made by mixing:
A weak acid and its conjugate base. OR a weak base and its conjugate acid
