From the equation used in this answer: Calculating charge on amino acid from pKa

$$\alpha=\frac{1}{10^{\mathrm pK_\mathrm a-\mathrm{pH}}+1}$$

Degree of dissociation of weak acid is $\alpha$. However, when it comes to weak base, degree of dissociation is $1-\alpha$. What is the explanation behind this?

  • 1
    $\begingroup$ I think this is because $\alpha$ is defined from $\ce{HA <=> A- + H+}$; which for a base would be exactly reversed. Not sure enought about it to answer, though. $\endgroup$
    – Jan
    Commented Oct 2, 2016 at 22:28
  • $\begingroup$ @Jan is almost certainly correct. For consistency, we looking at the equation he wrote. Same reason we generally look at pH instead of pOH. $\endgroup$
    – Zhe
    Commented Nov 20, 2016 at 20:45


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.