# Why is iodic acid a stronger acid than nitric acid?

Jun 4, 2016

Are you sure you mean iodic acid, $H I {O}_{3}$?
This site lists $p {K}_{a}$ of iodic acid at $0.75$. On the other hand, this site lists $p {K}_{a}$ of nitric acid at $- 1.4$. So given these metrics, nitric acid is a stronger acid than iodic acid.
You might mean to compare periodic acid, $H I {O}_{4}$, which should be a stronger acid than iodic acid (why?). For comparison, this site lists $p {K}_{a}$ of $H C l {O}_{4}$ at $- 15.2$. $H I {O}_{4}$ should be more strongly acidic (I could not find the metrics for this acid). Can you quote the oxidation state of iodine in its oxo-acids?