Sapling 9

[IreneSeo3F]

Why is the predominant species neutral if the pH value is less than the pKa value?

[Rachael Cohen 3G]

At pH values below the pKa, the protonated species of HA will become more predominant. HA is neutral. A- is the only charged species in the solution.

[JoshMoore2B]

Why is the predominant species neutral if the pH value is less than the pKa value?

Think of it this way:

pKa is a measure of a strength of an acid. When pH goes below pKa (that is, the acidity of the solution becomes stronger than the pKa), then the pKa won't be able to "compete" with the strength of the solution, and so it stays protonated and neutral.

[Jaclyn Schwartz 1I]

If the pH goes below pKa, that means the acidity of the solution becomes stronger than the pKa. When this occurs, the protonated species of HA will become more predominant, HA becomes neutral and A- is charged.

[Rose_Malki_3G]

This is because if the ph is lower than the pKa value it means that the surrounding solution is more acidic than the actual species, therefore it the species will not deprotonate and will remain neutral

[Chinmayi Mutyala 3H]

If the pH is less, the solution the acid is in is more acidic so it won't deprotonate in the solution. The solution already has a high hydrogen ion concentration so it won't be able to add hydrogen ions easily which is why it remains neutral.

[Alexis Sanft 1E]

What does it mean to be a "predominant" species?

[Alexis Sanft 1E]

Also, do we need to do any actual calculations if the pkA is given and the pH is given?

[Ranen_Chang_2G]

Also, do we need to do any actual calculations if the pkA is given and the pH is given?

To your questions, predominant species is the species where there is most of. In the acidic solution, the neutral HA is more. You do not need to calculate anything, just compare the values to each other.

[MichaelRaad_1F]

What does it mean to be a "predominant" species?

I'm pretty sure it just means that there is more of it or it is the most basic/acidic in solution.

[Nick Saeedi 1I]

if the pH is less than the pKa the HA concentration is the highest so it will be neutral.