Polyprotic Acids

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Ryan Chang 1C
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Joined: Sat Aug 24, 2019 12:17 am

Polyprotic Acids

Postby Ryan Chang 1C » Mon Feb 10, 2020 9:20 pm

How do you know if you can ignore the second ionization when calculating the pH of polyprotic acids?

Ryan Lee 1E
Posts: 50
Joined: Sat Aug 17, 2019 12:16 am

Re: Polyprotic Acids

Postby Ryan Lee 1E » Mon Feb 10, 2020 9:31 pm

I think generally, if Ka1 is 10^3 times bigger than Ka2, then you can ignore the second deportation. (you can double check this really quickly for yourself on test if it comes to it) To my knowledge, the most common acid that you will need to calculate the second deportation for is H3PO4.

Ryan Chang 1C
Posts: 105
Joined: Sat Aug 24, 2019 12:17 am

Re: Polyprotic Acids

Postby Ryan Chang 1C » Mon Feb 10, 2020 9:43 pm

Just found a section in the textbook that says that the only polyprotic acid that we would need to calculate the concentrations for the second deprotonation is sulfuric acid. Why do we need to do the same for H3PO4?

Ryan Lee 1E
Posts: 50
Joined: Sat Aug 17, 2019 12:16 am

Re: Polyprotic Acids

Postby Ryan Lee 1E » Mon Feb 10, 2020 9:51 pm

Ryan Chang 1C wrote:Just found a section in the textbook that says that the only polyprotic acid that we would need to calculate the concentrations for the second deprotonation is sulfuric acid. Why do we need to do the same for H3PO4?

I just looked back and yeah, you're right. I was looking at the 20L HW and got the two mixed up in my head my bad.


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