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Polyprotic Acids

Posted: Sun Feb 17, 2019 11:06 pm
by Rebecca Altshuler 1D
When writing out K for a polyprotic acid, do we include both versions of the conjugate base in the expression or just one?

Re: Polyprotic Acids

Posted: Mon Feb 18, 2019 10:57 am
by Elaine Pham 2E
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.

Re: Polyprotic Acids

Posted: Mon Feb 18, 2019 1:17 pm
by Jesse Kuehn 1B
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

Re: Polyprotic Acids

Posted: Mon Feb 18, 2019 2:55 pm
by Jayasuriya Senthilvelan 4I
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.

Re: Polyprotic Acids

Posted: Mon Feb 18, 2019 4:47 pm
by Karan Thaker 2L
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.

Re: Polyprotic Acids

Posted: Mon Feb 18, 2019 5:55 pm
by Aiden Atoori 1C
You have to express the conjugate acid of the acids that you are given.