I^- H5IO6 BrO2 HClO I2
Which could not disproportionate?
To disproportionate, one atom of an element must be oxidized and another atom of the same element must be reduced.
I^- is already at it lowest oxidation state; it can't go lower. not possible.
H5IO6. I is +7 in this compound which is the highest it can go. not possible.
HClO. Cl is +1 here, it can go up as well as down. possible if conditions are right.
etc. A caution here. Just because it is somewhere in the middle of its oxidation state range doesn't mean it WILL disproportionate. Conditions (I look at the Eo values) must be right.
To determine which compound could not undergo disproportionation, we need to understand what disproportionation is. Disproportionation is a chemical reaction where an element or compound both oxidizes and reduces itself simultaneously.
To identify the compound that cannot undergo disproportionation, we need to check if any of the compounds in the given list consist of different oxidation states of the same element. If a compound has only one oxidation state of an element, it cannot undergo disproportionation.
Let's examine each compound in the list:
1. I^- (Iodide ion): The iodide ion has an oxidation state of -1. Since it only has one oxidation state, it cannot undergo disproportionation.
2. H5IO6 (Periodic acid): Periodic acid has iodine in different oxidation states, +1 and +7. When iodine ionizes, it donates electrons and oxidizes itself to +7.
3. BrO2 (Bromine dioxide): Bromine dioxide has bromine in the +4 oxidation state. Similarly to iodide, bromine only has one oxidation state and cannot undergo disproportionation.
4. HClO (Hypochlorous acid): Hypochlorous acid has chlorine in the +1 oxidation state. Like iodide and bromine, chlorine cannot undergo disproportionation.
5. I2 (Iodine): Iodine is an element and exists as I2 in its elemental form. It does not have multiple oxidation states and, hence, cannot undergo disproportionation.
From the given compounds, only H5IO6 (Periodic acid) consists of iodine in different oxidation states and can undergo disproportionation, while the other compounds (I^-, BrO2, HClO, and I2) cannot.