Ka vs pKa

[305561744]

Can someone explain the differences between these two for acid base reactions? Which one involves taking the log?

[Sohan Talluri 1L]

K_A is the equilibrium constant for the acid and is calculated by K_A = [H+][A-] / [HA]. pK_A refers to the "power of K_A" and is calculated by pK_A = -log₁₀ (K_A).

Hopefully this helps and please correct me if there are any mistakes.

[Sunny Hou 2I]

Hi,
So the difference between Ka and pKa is that Ka is the dissociation constant for acid and represents the strength of the acid, whereas pKa is the -log of the Ka value. These two are inversely related, so the larger the Ka, the smaller the pKa and thus the stronger the acid is. This is the same principle for bases as well, with Kb and pKb. I remember it as p=-log, for ease of understanding.

Hope this helps.

[Natalie Swerdlow 3K]

If you're trying to classify an acid from Ka and pKa, the higher the Ka value, the stronger the acid. Therefore, the lower the pKa value, the stronger the acid as well. This is the same with Kb and pKb for bases as well.

[oliviahelou]

Ka: a strong acid has a high Ka value and a weak acid will have a lower Ka value.
pKa: it is kind of the opposite, the lower the pKa value, the stronger the acid.

Logically, it would be the same for the kb and pKb values for bases

[Hannah_Pon_1F]

pKa is the -log(Ka). One of the reasons we use pka is to compare this value directly to the pH. This tells you if there are more charged or neutral species present.

[Coraly De Leon]

Hello,
Just as my peers mentioned,
Ka will be the disassociation acid constant that will represent the strength of the acid whereas pKa is the -log of Ka. They both have an inverse relationship: the larger the Ka, the smaller the pKa value.

[elletruchan2I]

When a p is attached to something, it always means that the negative log is being taken of that number. Other than this, both Ka and pKa convey the same information of how strong an acid is, but a strong acid will be smaller for pKa and larger for Ka.

[Wilson Zheng 1L]

Ka is the equilibrium constant for acids! pKa is the -log value of Ka. A lower pKa equates to a higher Ka, and the higher the Ka, the stronger the acid!

[Madison Nguyen 3L]

Ka is simply the negative antilog of the pKa as the dissociation acid constant, whereas pKa is the negative log of the Ka.

[Hailey Sarmiento 3E]

Ka is the equilibrium constant for an acid reaction (Kb is the same but for a base reaction) and the pKa is the negative log of the Ka (pKa = -log(Ka)). i like to think of this relationship as similar to the relationship between pH and [H3O+] or pOH and [OH-]

[Srikar_Chintala_1E]

Ka is the equilibrium constant for the acid which you would set up as a fraction. However, pKa is the -log of the Ka value.

[Natasha]

Ka is representative of the disassociation constant which is representative of the strength. On the other hand pka is the -log of Ka and there is an inverse relationship between Ka and pKa.

[Amanda Tran 1D]

Generally speaking, "p" implies the -log of something. Ka is the equilibrium/dissociation constant of an acid, so pKa = -log (Ka).

[sadiebrebes]

Can someone explain the differences between these two for acid base reactions? Which one involves taking the log?

Hello, as mentioned before, the Ka is the equilibrium constant, where the pKa is the negative log of the Ka. They are inversely proportional, when one goes up the other goes down. The higher the Ka the Stronger the acid and the smaller the Pka the stronger the acid. The higher the Ka, the more the acid dissociates.

[Joseph Lee]

Ka is the actual constant and pKA is the negative log of that

[Diana Avalos]

Ka is the equilibrium canstant, its Kb for the base, and pKa is the -log of pKa, and pKb is the negative log of Kb