Danial N. answered • 01/06/21
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Experienced MCAT Tutor/Medical Student| 99th percentile MCAT scores
You use the Henderson-Hasselbach Equation.
pH = pKa + log { [A- ] / [HA] }
Take the negative log of Ka (acid dissociation constant) if needed to find pKa.
[A-] and [HA] are the concentrations of the acid and the conjugate base given in units of Molarity (M)
Zach D.
Thank you!
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01/07/21
J.R. S.
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This is exactly correct if you happen to have a buffer. What if you have a salt, like NaF? Then you look at hydrolysis of F- and use the Kb for F- without the HH equation. If you had NH4Cl, you would look at the hydrolysis of NH4+ and use the Ka for NH4+. So, I think the answer really depends on what the solute is.
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01/07/21
Danial N.
Thank you J.R. You make a good point and are absolutely correct.
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01/07/21
Danial N.
I should clarify: [A-] is the conjugate base [HA] is the acid for example in Hydrofluoric Acid: [HF] is the acid, [F-] is the conj. base01/06/21