Acidity question

[deleted783484]

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Rank the acidity of H3po4, h3po2 and h3po3.

I thought that the higher the oxidation state of the central atom the more acidic it is but in this example it's the opposite?
Thank you so much

@aldol16

 

[aldol16]

This is a case where the explanation is more advanced than you need to know for the MCAT. It's also one of the rarer exceptions to the rule you state and so you don't need to know this. A complete understanding would require understanding of MOs.

 

[ultraviolet_catastrophe]

The stronger the acid, the more stable the conjugate base and vice versa. The more O's provide more resonance-stabilization.

 

[aldol16]

The stronger the acid, the more stable the conjugate base and vice versa. The more O's provide more resonance-stabilization.

This particular acid follows the reverse trend you would predict from resonance alone.