What is the relationship between pKa to the pH or pOH?

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What is the relationship between pKa to the pH or pOH?

Postby Chem_Mod » Sun Aug 21, 2011 12:15 pm

Question: Is there any relation between pKa and the pH or pOH? The smaller the pKa, the stronger the acid. The lower the pH, the stronger the acid. But why are certain acids with very small pKa (ex trichloroacetic) still considered weak acids?

Chem_Mod
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Re: What is the relationship between pKa to the pH or pOH?

Postby Chem_Mod » Sun Aug 21, 2011 12:15 pm

Answer: The relationship between pKa and pH is given by the Henderson-Hasselbach equation. Acid strength increases with decreasing pKa. A strong acid is not represented with an equilibrium constant because it is assumed to dissociate completely (Ka is "infinite," if you want). Weak acid does not dissociate completely.


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