Oxoacids

[Kylie McCauley 1D]

Hi,

In oxoacids, it appears that electronegativity trumps atomic radius, is this correct? for example, The acids : HClO, HBrO, and HIO are strongest to weakest in that order. If they were normal acids without the oxygen, their relative strength would be in the opposite order. And overall, are oxoacids considered weak acids, because none of the acids I stated are present on the strong acids list in the book.

[Will Skinner]

Yes, I think so. With oxoacids, the electronegativity of the other atom bonded to O determines the relative strength. The more electronegative it is, the weaker/more polar the O-H bond, so it would also be a stronger acid because the H proton is given up more easily.

[Jeffrey Hablewitz 2I]

The hydrogen is bonded to the oxygen in each oxoacid, so atomic radius is not really considered when comparing the strengths of these acids (the O-H distance is similar in each acid). Like you said, chlorine has the highest electronegativity (and therefore the strongest electron-withdrawing effect) of the halogens in each acid. Because of this, HClO^- is the most stable conjugate base and HClO is the strongest acid.

[Catie Donohue 2K]

When determining the strength of acids, size is correlated with electronegativity in a group since a bigger atom is more likely to give up its outer electrons - therefore I believe both oxoacids and regular acids are reliant on electronegativity. My guess is the trends in oxoacid strength are due to the relative strength of the Cl-O bonds (or whatever that middle element is with O), which weakens the H-Cl bond accordingly and makes it a stronger acid, but if anyone can give more detail about why the oxoacid trends are that way I'm still a little confused on the specifics. Thank you!