acids

[Maribel 1E]

Why does a lower pKa value mean that the acid is stronger?

[Emma MacLachlan 1D]

Similar to how for pH, a lower pH means that something is more acidic, a lower pKa value means that the acid is stronger.

[Anthony Lau-Xiao 1E]

A lower pKa value means that the acid is stronger because on the pH scale, a lower value means it is more acidic. pKa comes from taking the -log of an acid (pKa = -log(Ka)), so if Ka = 10^-3, then pKa would be -log(10^-3), so pKa would be 3, which means it is a strong acid.

[Elliana_Tsang_1L]

Here's how I like to think about it: as we know, Ka = [products]/[reactants], where the reactant is the weak acid and the product is H3O+ and the conjugate base. With stronger acids, they dissociate more into H3O+ and their conjugate base, so the products are favored. This increases the Ka value, and since the pKa value is the inverse relation to Ka, it becomes small. A small pKa means a larger Ka value.

[Yasmine_B_1H]

Hello,

This was a difficult concept for me to grasp for a little. It is important to remember that Ka=[products]/[reactants], products will be the H3O and the conjugate base meanwhile the reactant is the weak acid. Remember that with stronger acids they are more likely to disassociate, so there will be more H3O and more conjugate base. So this reaction will favor the products since there is more products. This will then cause the Ka value to increase. Remember pKa is the inverse of Ka, so pKa will be small when Ka is large.

So, a lower pKa will be a stronger acid because of the strong dissociation of the acid.

[Yasmin Moosavy1A]

Because pKa is the -log of Ka and Ka is the equilibrium constant for an acid (so it shows how much of the acid has dissociated when it forms its products). When there is the higher the Ka value (more positive)the lower the pKa since it is the -log. A more positive Ka means more dissociation in the products. so if Ka was something x 10^-4 the -log (pKa) would be 4, and that is stronger than a acid with a ka of 10^6 which its pkA would be 6 which means it is less dissociated, thus smaller ka, and bigger pKa (less acidic).

[Sarah Wang 2G]

This is usually how I think of it:
Ka is the acid dissociation constant, so the bigger the Ka is, the more that acid will dissociate in a solution and the stronger the acid is. pKa measures the tendency of the acid to keep its proton, so the smaller it is, the stronger the acid and the more likely it will dissociate. Therefore, Ka and pKa have an inverse relationship, which can be seen through the formula pKa = -log(Ka).

[Althea Bravo 3E]

The lower the pKa, the higher the Ka will be. Since Ka is the acid dissociation constant, a higher value means it dissociates more, thus is more strong. So: low pKa = high Ka = stronger acid

[Brandon_G_1H]

Hello! Like other replies, a lower pKa means that the compound is a strong acid. Similarly, high Ka is also indicative of a strong acid.

[Avani Pammidimukkala 2F]

A lower pKa value means that an acid is stronger because it means that the acid is more ready to give up a proton. However, if the acid had a higher pKa value, then it would be harder to release the proton.

[Anahi C 2F]

A lower pKa value means that the acid is stronger. A lower value for pH means it is more acidic. In order to make sense of this, I often think of it mathematically using the equation pKa = -log(Ka). If Ka= 10^-4, then the pKa would be -log(10^-4), so pKa would be 4, which means it is a strong acid.

[Andres Ibarra 2F]

Hi!
A lower pka value is related to a low pH. So the lower the pH, the more acidic a solution is. Similarly, a lower pka value means that the acid is strong. low pka will equal a high Ka which will be a strong acid.

[105747606]

Yes, a lower pKa means an acid is stronger, similar to how a lower pH means an acid is stronger.

[Sanjay Annamalai 3E]

The pka value is directly related to the pH value, so a lower pka = lower pH = more acidic.

[505400967]

Just as pH is the negative log of the H+ concentration. pKa is the negative log of the Equilibrium constant for the dissociation of an acid. Mathematically, this makes it so that the stronger the acid, the stronger the Ka, and the lower the pKa. pKa describes acid dissociation using small decimal numbers.

The reason pKa is used is because it describes acid dissociation using small decimal numbers. The same type of information may be obtained from Ka values, but pKa is easier to work with!

[samaagwani-disc2L]

A low pKa value indicates a strong acid just like how a low pH value indicates a strong acid. I like to make that connection to help me remember. Hope this helps:)