Ka and Ka2

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CHEM 14B Lover
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Joined: Fri Sep 28, 2018 12:19 am

Ka and Ka2

Postby CHEM 14B Lover » Fri Mar 15, 2019 5:08 pm

Will be asked to find pH given Ka and Ka2 of a diprotic acid? How would we set up an ice tablee in that case?

David S
Posts: 54
Joined: Fri Sep 28, 2018 12:15 am

Re: Ka and Ka2

Postby David S » Fri Mar 15, 2019 5:20 pm

You first set up ice table and Ka expression for the diprotic acid, and then you solve for [H+]and [HA-]. You then set up separate ice table and Ka2 expression for the dissociation of HA- into A2- and H+ using the [H+] and [HA-] found in part 1. Solve for new [H+] and then turn it into pH.

Note that usually the second and third dissociation s add very little H+ to the H+ formed by first dissociation.

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