## pH and buffer solutions

This is not a homework question, so I cannot give exact values or anything, sorry.

If we have to make a buffer solution, and we know the pH and the pKa of the acid we are going to use, would it be true to say that if the pH < pKa, we will need more of the weak acid than salt? If pH > pKa, we would need more salt?

Same thing for the pKb and pOH (14 - pH), would we need more salt if the pKb was bigger? More base if the pKb was smaller?

If we have to prepare a buffer with a target pH, and pH = pKa, we need the same quantity of acid and salt respectively, correct? (so that pKa = pH - log1, since log1=0)
BUT if we have pKa = 14 - pKb, what would be the reasonning then? I have a bit of trouble visualizing all that.

Thank you,

~J.
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 Quote by future_vet If we have to make a buffer solution, and we know the pH and the pKa of the acid we are going to use, would it be true to say that if the pH < pKa, we will need more of the weak acid than salt? If pH > pKa, we would need more salt?
OK

Think in terms - add more acid to lower pH

Borek
--
General Chemistry Software
www.pH-meter.info
 So my first part would be right? If the pH is lower than the pKa we need more acid? Thanks, ~J.