KA and pKA

[Alvin Lai 3J]

In Dr. Lavelle's Friday lecture, he talked about KA and pKA. I do not really understand what these are, can someone explain to me? Also, are we going to be calculating these numbers for the final?

[Giselle Granda 3F]

KA is the acid dissociation constant which tells how strong the acid is, while pKA is simply the negative log of that value. When the Ka is large, the acid is strong, when it is small, the acid is weak. Hope this helps!

[IsaacLaw1E]

There shouldn't be any calculations that involve finding KA or pKA unless it's a conversion between the two. However, there will be calculations involving strong acids and bases, which completely dissasociate.

[Jordi M 2I]

Also remember that the product between the concentration of H30+ molecules and the concentration of OH- molecules will always be 1*10^-14. Some questions may ask you to find the H3O+ conc. by giving you the OH- conc. Just useful to know (:

[dana hu 1B]

Hello!
Ka = [H+] [A-]/ [HA]
Ka is the measures the strength of an acid. A stronger acid will have a greater [H+] concentration and hence a greater Ka.
A larger Ka means a smaller pKa
pKa = - log Ka

[Kelly Singh]

KA measures the strength of an acid whereas pKA is the negative log of that value. It's just an easier and more convenient way to refer to the KA value as far as I know. =)

[Michael Sun Dis 3G]

Ka is the acid dissociation constant, while pKa is the negative log of the Ka value. Both can be used to infer the strength of an acid, though they do have an inverse relationship.

[Joshua Eidam 2A]

KA measures the strength of an acid whereas pKA is the negative log of that value. It's just an easier and more convenient way to refer to the KA value as far as I know. =)

Does a higher Ka value represent a stronger acid or is it not that simple?

[IsaacLaw1E]

KA measures the strength of an acid whereas pKA is the negative log of that value. It's just an easier and more convenient way to refer to the KA value as far as I know. =)

Does a higher Ka value represent a stronger acid or is it not that simple?

That is correct. Higher Ka values means more disassociation, which means stronger acid.

[jessicasilverstein1F]

Ka is the acid dissociation constant. pKa is the negative log of the Ka value. When Ka increases the strength of the acid also increases and the pka decreases.

[Mia Meza]

KA measures the strength of an acid whereas pKA is the negative log of that value. It's just an easier and more convenient way to refer to the KA value as far as I know. =)

Does a higher Ka value represent a stronger acid or is it not that simple?

Yup, the higher the Ka value the stronger the acid.... higher the Kb value the stronger the base. However, the higher the Pka value, the weaker the acid and the same applies to the base.

[FrancescaHawkins2H]

I don't believe we will need to directly calculate Ka and pKa, but it would be best to know the relationships between the two, and understand how they relate to the strength/weakness of acids, as explained above.

[Charmaine Ng 2D]

Ka measures the dissociation of a weak acid by calculating the concentration of its products over its reactants, while pKa is just the negative log of that for simplicity's sake!

[Jack_Pearce_2H]

Ka is just a term to measure the strength of an acid. It is proportional to pH in that the lower the pKa (-log(Ka)), the stronger the acid. He will elaborate more in 14B but basically it is how much an acid (strong or weak) will dissociate in water.

[Sam Wentzel 1F 14B]

Both values correlate to acid strength. The lower the KA / pKA the stronger the acid.

[jasmineculilap_3F]

Ka is the acidity constant and pKa is the -log of Ka. Ka = [H+][A-]/[HA]. Both can be used to find out how strong an acid is. A higher Ka means a lower pKa and stronger acid while a lower Ka means a higher pKa and weaker acid.

[Sean Wang 1F]

A bigger Ka value corresponds to a greater strength of an acid, while a bigger pka value corresponds to a weaker strength of an acid.

[Bella Bursulaya 3G]

The larger the Ka value, the stronger the acid because this means that the products outweigh the reactants, and the lower the pKa.

[JonathanM]

Hey!
So the Ka value describes the ratio of how much of the acid is split into ions versus how much of the acid remains unsplit, so a higher Ka is more acidic, and the pKa describes the equilibrium pH the substance would reach when placed in pure water. If the solution that the substance is placed into has a lower pH than the pKa of the substance then more of it will remain neutral, whereas if the pH is higher than the pKa more of the substance will be charged and split into ions.

[Malakai Espinosa 3E]

Ka is a value for the ratio of products to reactants. pKa helps us tell the strength of a weak acid, and this is determined by taking the negative log of the Ka value.