Diprotic Acids

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Bailey Giovanoli 1L
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Joined: Wed Sep 30, 2020 9:50 pm

Diprotic Acids

Postby Bailey Giovanoli 1L » Sun Jan 17, 2021 12:38 am

Just to clarify, you can ignore the second or even third deprotonation in polyprotic acids when the first Ka is greater than the Ka in the second and third proton transfer.

Victor Qiu 1C
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Joined: Wed Sep 30, 2020 9:59 pm
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Re: Diprotic Acids

Postby Victor Qiu 1C » Sun Jan 17, 2021 8:58 am

I think in most of the times, yes. This is because the second Ka is often much smaller than the first Ka.
Take H3PO4 as an example, Ka1=7.1 × 10-3, Ka2=6.3 × 10-8, Ka3=4.5 × 10-13. The difference between Ka1 and Ka2 is at the scale of 105. Thus, I think the second Ka can often be ignored.

Eliot Kagan 2G
Posts: 85
Joined: Wed Sep 30, 2020 10:08 pm

Re: Diprotic Acids

Postby Eliot Kagan 2G » Sun Jan 17, 2021 1:38 pm

To add on, I think you have to consider the 2nd ka value when doing strong acids like Sulfuric acid H2SO4.

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