Polyprotic Acids

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Rebecca Altshuler 1D
Posts: 61
Joined: Fri Sep 28, 2018 12:15 am

Polyprotic Acids

Postby Rebecca Altshuler 1D » Sun Feb 17, 2019 11:06 pm

When writing out K for a polyprotic acid, do we include both versions of the conjugate base in the expression or just one?

Elaine Pham 2E
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Joined: Fri Sep 28, 2018 12:28 am
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Re: Polyprotic Acids

Postby Elaine Pham 2E » Mon Feb 18, 2019 10:57 am

For polyprotic acids, the K for the reactions are different for each time, so you would only write the conjugate acid in the specific reaction you are looking at to find the equilibrium constant.

Jesse Kuehn 1B
Posts: 40
Joined: Wed Nov 14, 2018 12:23 am

Re: Polyprotic Acids

Postby Jesse Kuehn 1B » Mon Feb 18, 2019 1:17 pm

you have to write out each equation separate as though the two reactions are independent, making two different ice tables, however with the second ice table, you have to be sure to add the hydronium or h+ ions that were created in the first reaction so the initial concentration of hydronium in the second ice table will not be zero

Jayasuriya Senthilvelan 4I
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Joined: Thu Jan 10, 2019 12:17 am

Re: Polyprotic Acids

Postby Jayasuriya Senthilvelan 4I » Mon Feb 18, 2019 2:55 pm

For polyprotics you have multiple Ka values depending on the number of hydrogens. Each ka after the initial one is smaller (because its hard to separate a H+ from a negatively charged ion). Sulfuric acid is a strong acid during its initial deprotonation. Afterwards, its a weak acid. Other acids (unlike sulfuric) are weak upon their initial deprotonation, and each subsequent deprotonation is weaker. Check the book section on polyprotics for more information.

Karan Thaker 2L
Posts: 75
Joined: Fri Sep 28, 2018 12:26 am

Re: Polyprotic Acids

Postby Karan Thaker 2L » Mon Feb 18, 2019 4:47 pm

I write it out as Ka1, Ka2, Ka3... so on and so forth. Use the respective conjugate bases and acid each time you do the step.

Aiden Atoori 1C
Posts: 67
Joined: Fri Sep 28, 2018 12:24 am

Re: Polyprotic Acids

Postby Aiden Atoori 1C » Mon Feb 18, 2019 5:55 pm

You have to express the conjugate acid of the acids that you are given.

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