What does pka equal

And it just has a special name, 'cause it happens to be for the dissociation of an acid. And as you can see up here, an acid and its conjugate base are just related by the fact that the acid has an extra H.

We can rearrange the Henderson-Hasselbalch equation to get a lot of different kinds of information. One kind of problem you see a lot is for some buffer, you know, they might ask you, oh, what's the pH? The other thing that you can use the Henderson-Hasselbalch equation to tell you is the relationship between A minus and HA which is something you might wanna know.

A lot of times, you just wanna know, you know, what's in your solution, depending on what you wanna do to your solution, if you wanna add things to it, maybe you wanna add some acid, you wanna add some base. You wanna know what's going on. The Henderson-Hasselbalch equation gives you a really quick and easy way of doing that.

So what we're gonna do, is we're gonna rearrange this equation to solve for this ratio that we might be interested in. And I don't know about you, but I actually find, well, laughs I find logs not super-intuitive sometimes. So I'm actually going to get rid of the log by raising both sides to the 10th power. So what does this tell us? It may not look like it tells us a whole lot more, but actually, it tells us a lot.

It tells us about the relative relationship and size between A minus and HA concentration. So if we look at this, we can derive a couple relationships. So let's go ahead and look at all the possible scenarios for these three things. So anything to the zeroth power is equal to one. If we compare this to a weak acid where the oxygen is bound to a carbon atom as in carboxylic acids the oxygen is bound to the hydrogen and carbon atom. In this case, the oxygen is not bound to another electronegative atom.

Thus the H-O bond is not further destabilized and the acid is considered a weak acid it does not give up the proton as easily as a strong acid. Figure 2. The strength of the acid can be determined by the electronegativity of the atom the oxygen is bound to. For example, the weak acid Acetic Acid, the oxygen is bound to carbon, an atom with low electronegativity. In the strong acid, Hypochlorous acid, the oxygen atom is bound to an even more electronegative Chloride atom.

Attribution: Erin Easlon. In Bis2A you are going to be asked to relate pH and pKa to each other when discussing the protonation state of an acid or base, for example, in amino acids. How can we use the information given in this module to answer the question: Will the functional groups on the amino acid Glutamate be protonated or deprotonated at a pH of 2, at a pH of 8, at a pH of 11?

In order to start answering this question we need to create a relationship between pH and pKa. The relationship between pKa and pH is mathematically represented by Henderson-Hasselbach equation shown below, where [A-] represents the deprotonated form of the acid and [HA] represents the protonated form of the acid.

Figure 3. The Henderson-Hasselbach equation. This means that when the pH is equal to the pKa there are equal amounts of protonated and deprotonated forms of the acid. For example, if the pKa of the acid is 4. Since organic reactions can be performed in non-aqueous environments, the pH can exceed 14 and organic compounds can have pKa values above It is a variation on that line from the Wizard of Oz, "We don't live in water anymore.

It is a very good idea to commit to memory the approximate pK a ranges of the compounds above. If you are asked to say something about the basicity of ammonia NH 3 compared to that of ethoxide ion CH 3 CH 2 O - , for example, the relevant pK a values to consider are 9. From these numbers, you know that ethoxide is the stronger base. Do not make the mistake of using the pK a value of this is the pK a of ammonia acting as an acid , and tells you how basic the NH 2 - ion is very basic!

Biochemistry and organic chemistry texts often list the value as These texts have incorrectly factored the molar value for the concentration of water into the equilibrium constant. The correct derivation of the equilibrium constant involves the activity of water, which has a value of 1. While this course begins with single functional groups, we will eventually work with interesting compounds containing multiple functional groups.

Recognizing which hydrogens can be ionized as acidic protons and which hydrogens can NOT, is a useful skill.