General Chemistry - Polyprotic Acid Ion Concentration

[Typical Average Student]

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I was reviewing some of Chad's notes for Gen Chem and he says for polyprotic acids (ex. H2SO4) only 1 proton dissociates strongly, the other weakly, which is why if you were given 0.1M of H2SO4 you would only have 0.1M [H+] and not 0.2M [H+].

I was working through a practice problem in Kaplan and they incorporated the dissociation of both protons which would give you 0.2M [H+] in their calculation.

My question is which concept will the DAT use for polyprotic acids?

 

[XZeRO]

Depends how the question is posed.

If it asks for complete neutralisation of the acid, then you would need to use 0.2M. If it is asking you for how much H+ is in solution after H2SO4 reaches equilibrium, for example, then it would be closer to 0.1M.

 

[DAT Destroyer]

I was reviewing some of Chad's notes for Gen Chem and he says for polyprotic acids (ex. H2SO4) only 1 proton dissociates strongly, the other weakly, which is why if you were given 0.1M of H2SO4 you would only have 0.1M [H+] and not 0.2M [H+].

I was working through a practice problem in Kaplan and they incorporated the dissociation of both protons which would give you 0.2M [H+] in their calculation.

My question is which concept will the DAT use for polyprotic acids?

Hope this helps.

Dr. Romano

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