Pka and acidity

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Dental2000

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How is pKa related to acidity?

I say the lower the pKa the more acidic the molecule??

not sure if its rite
 
That's correct, the lower the pKa, the more acidic.

This is opposite of Ka: the higher the Ka, the more acidic.

Reason why is because pKa = - log Ka

Btw, p of anything = - log of something, (such as i.e. pH = - log [H+])
 
Right. pKa is the neg. log of Ka and is most commonly used for buffers and Henderson Haselbauch (pH = pKa + [A-]/[HA],. pH is the neg. log of the H+ concentration. The higher the Ka the stonger the acid, and therefore the lower the pKa the stronger the acid. Same goes for pKb and Kb. p just simply means the neg. log.
 
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