pKa and Ka

[Chelsea Culi 3F]

What do the pKa and Ka values tell us about the molecule?

[Lauren Woodward 1I]

Ka is the acid dissociation constant, so a large Ka would mean that the acid dissociates more completely in water. The negative common log of Ka is pKa. The value of pKa can tell you the strength of an acid. A low value of pKa means the acid is more likely to give away protons (H+), and is therefore stronger.

[Allison Mercado-3F]

Is the pKa just like the pH?

[Konmal Ali 1G]

pKa and pH are related, but they are not exactly the same. By knowing the pKa value of a molecule, one can understand how that molecule will act at a certain pH. Furthermore, the pKa value can allow you to calculate the pH which is needed for a molecule to accept a proton or to donate a proton. I hope this helps!

[Kurosh Zamiri 1I]

Hi! Ka refers to the acid dissociation constant, which is only used in the case of weak acids. If a Ka is mentioned, then you know the acid is weak. A high Ka implies higher dissociation of the acid in water. The pKa is the negative log of the Ka. Therefore, a lower pKa means that the acid is stronger. Hope this helps!

[Anubhav_Chandla1G]

Ka and pKA are related because Ka is the acid dissociation constant of a compound while pKa is the negative log of the Ka. The higher the Ka, the higher the acidic character, and the lower the pKA the higher the acidic character. This is because the pKA provides the PH level of the acid.

[Hailey Jeon]

pKa = -log Ka
Higher the pKa value, the weaker the acid, therefore the pH is higher.

[hanniaghernandez]

thank you so much to everyone for explaining this concept! I was also having trouble understanding the difference between both!!

[Diego Gonzalez 1H]

pKa value is used to indicate the strength of an acid. Ka is the acid disassociation constant.

[Sarah Hong 2K]

When something is a low pKa, it is more acidic and has a higher Ka. When something has a high pKa, it is less acidic and has a lower Ka. If pKa=4.22, Ka=10^-4.22.

[Vashe Sundar 3H]

They're both related in that they both tell you the relative strength of an acid. The only difference is that pKa is the -log of Ka, so their relationship is inverted, meaning that when Ka is larger, the pKa is smaller, and the acid is stronger.