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IreneSeo3F wrote: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.
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 wrote: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.
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