Lesson 3.6 - Ka of mono- and polyprotic Acid
Date: Feb 9, 2022 08:59 AM Eastern Time (US and Canada)
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Date: Feb 10, 2022 09:01 AM Eastern Time (US and Canada)
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***Some comment on polyprotic strong acid H2SO4 and polyprotic weak acid H2CO3***
For example if we look at H2CO3, the Ka1 value is 10-7 (which is not that big), however its Ka2 value is 10-11. Relatively the second value doesn't impact the K value that much, and thus we use the Ka1 value as a decent approximation. This applies to most polyprotic acids, as in we will just be using the Ka1 value.
In the video sulfuric acid, H2SO4, was mentioned explicitly, because it is an exception to the rule. The Ka1 value on its own is large, and the Ka2 value is 10-2 which by itself is also significant in the equilibrium. As such, unlike most other acids with multiple Hydrogens, sulfuric acid has a high Ka2 which makes it strong.
Overall, acids that dissociative multiple times are weak and we can use Ka1 as an approximation because Ka2 is a considerably smaller number. H2SO4 is an exception, because both its Ka1 and Ka2 are big.Textbook 8.4 - pg516. Practice #1, 2; pg520. Practice #1, 2
pg521. Practice #1, 2; pg524. Practice #1, 2
pg525. #5, 7, 10