pKa#
- Page ID
- 21322
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pKa
The most common acid we will talk about in BIS2A is the carboxylic acid functional group. These acids are weak acids, meaning that they only partially dissociate (into H+ cations and RCOO-
Note that the key difference in the figure below between a strong acid or base and a weak acid or base is the single arrow (strong) versus a double arrow (weak). In the
- both forms of the conjugate acid or base (that is what we call the molecule that "holds" the proton - i.e. CH3OOH and CH3OO-, respectively in the figure) are present at the same time and
- the ratio of those two quantities can change easily by moving the reaction in either direction.
Figure 1. An example of strong acids and strong bases in their protonation and
In Bis2A you we ask you to relate pH and
To answer this
Figure 2. The Henderson-Hasselbach equation
A solution to this equation
Figure 3. This graph depicts the protonation state of acetic acid as the pH changes. At a pH below the
In BIS2A, we will look at the protonation state and
Figure 4. This graph depicts the protonation state of glutamate as the pH changes. At a pH below the
Attribution: Ivy Jose
Possible NB Discussion Point
What is the overall charge of free Glutamate at a pH of 5? What is the overall charge of free Glutamate at a pH of 10? In as much detail as you can, using the terms you've learned thus far in this course, describe the chemical change of glutamate’s predominant form as the pH changes from 5 to 10.