Acids, Bases, pHs, and Buffers Flashcards
Under what conditions is a buffer most effective?
when the concentration of a weak acid and its conjugate base are equal
A solution that resists changes in pH when perturbed by the addition of an acid or base
buffer
How can the bicarbonate system be simplified?
CO2 H+ + HCO3-
What is K/K(eq)?
[products]
________
[reactants]
forward and reverse rates are equal
Using magnitudes of K, what are the predicted concentrations of products and reactants?
Small K (<10^-3) = more reactants than products Intermediate K (10^-3 - 10^3) = equal amount of reactants and products Large K (>10^3) = more products than reactants
______ acids have large values for K
strong
pKa
-logKa
pH at which the weak acid/base is 50% ionized/50% unionized
pH is a measure of …
H+
pKa is a measure of…
dissociation
a stronger acid acid has a _____ pH and a _____ pKa
lower; lower
As the [H+] increases, pH ______
decreases
As the dissociation increases, pKa _____
decreases
If a molecule has a negative pKa, it has a ______ Ka
large
If a molecule has a small Ka, what do we know about the concentrations of the products and reactants?
more reactants than products
If a molecule has a small Ka, it has a _____ pKa
large
Henderson-Hasselbalch (Definition)
relates the pH of a solution of a weak acid to the pKaand extent of ionization of that acid
Henderson-Hasselbach (Equation)
pH = pKa + log([A]/[HA]) OR pH = pKa + log([unprotonated]/[protonated]) OR pH = pKa + log ([conjugate base]/[acid])
______ can be referred to as unprotonated, charged, or ionized form
conjugate base
______ can be referred to as protonated, uncharged, or unionized form
weak acid
What does Ka reflect?
The ionization of the acid
How is pKa related to buffering capacity?
indicates the pH where the substance will be most effective as a buffer – based on the side chain
Can charged or uncharged pass through the membrane more easily?
small uncharged molecules
