Second Deprotonations

[Rhona_McChesney_1F]

Hello,
I noticed problem 6.E.3 discusses second deprotonations, which I don't think we went over in class. Could someone explain how deprotonations work and when to look out for deprotonations?

[Sophia Olender 2J]

Deprotonation is basically just how the word sounds. A substance reacts, resulting in the loss of a proton (H+). Polyprotic acids (acids with more than one H+) can have second deprotonations because they lose one H+ in the first reaction and the second one in another. So look out for second deprotonations when you come across a polyprotic acid.

[kylanjin]

Second deprotonations are associated with polyprotic acids that have more than one H to donate like H2SO4. H2SO4 is a special case where its first deprotonation is complete, and so you have to use its 2nd deprotonation value when doing calculations with it. For normal polyprotic acids, their 1st deprotonation K value is what really matters since subsequent ones are so weak that don't affect the pH significantly.

[Sujin Lim 1H]

As mentioned above, second deprotonation is when an acid loses a H+ proton for the second time. This usually occurs to polyprotic acids, because polyprotic acids by definition have more than one H+ to donate. In general, you know a deprotonation has occurred if a species (such as an acid) has lost a proton.

[Brenda Tran 3C]

Deprotonation essentially refers to the transfer of a proton. A second deprotonation would therefore mean that the acid in the equation has donated two of its protons. This usually occurs for polyprotic acids or "more than one H+" acids.