In the HClO4 perchloric acid molecule, the oxidation state of chlorine is +7.To determine this, we can assign oxidation numbers to each atom in the molecule:1. Hydrogen H usually has an oxidation state of +1.2. Oxygen O usually has an oxidation state of -2.3. The sum of the oxidation states in a neutral molecule must equal the overall charge of the molecule, which is 0 in this case.Using these rules, we can set up an equation: +1 + Cl + 4 -2 = 0Solving for the oxidation state of chlorine Cl :1 - 8 + Cl = 0Cl = 7So, the oxidation state of chlorine in HClO4 is +7.