HCLO4 vs. H3PO4

[Ayush Ray 1I]

Which is the stronger acid and why

[lilymayek_1E]

HClO4 is the stronger acid. The comparison here is that you have to look at electronegativities, a quality that Cl is stronger in than P. Cl is more electronegative, which means it draws electrons closer to itself and delocalizes electrons. This pull pulls electrons from H, making it unfavorable for H to try and share the electrons that are being pulled away. H is more likely to disassociate from HClO4 than H3PO4, making it the stronger acid (H3PO4 is also just a naturally weak acid!)

[Joshua Eidam 2A]

I am confused as to why something that is more electronegative would result in the formation of a weaker acid. Would the H+ not be more attracted to Cl- if it is so electronegative, thus making it harder to break away and therefore an overall weaker acid?

[Chudi Onyedika 3A]

I am confused as to why something that is more electronegative would result in the formation of a weaker acid. Would the H+ not be more attracted to Cl- if it is so electronegative, thus making it harder to break away and therefore an overall weaker acid?

When there are more than two other atoms in a compound, electronegativity will pull the electrons away from the hydrogen.

[kareena_prasad]

HClO4 is stronger than H3PO4 because chlorine is more electronegative than phosphorus.