Question

Why do the oxidation states of dioxygen and dihydrogen alter when these materials react?

Answer 1

Because hydrogen is a reductant, and oxygen is an oxidant. Water, `H_2O`, is the product of such redox processes when hydrogen burns in air.

Explanation:

Elemental hydrogen, `H_2`, and elemental `O_2`, are both zerovalent, i.e. their oxidation states are `0`. Hydrogen will tend to be oxidized, and oxygen tends to be reduced. When such redox processes occur, water is the product of the redox reaction. Is this sufficient?

We can write the stoichiometric equation and SUPERSCRIPT the oxidation numbers...

`stackrel(0)H_2 + 1/2stackrel(0)O_2(g) rarr stackrel(""^(+I))H_2stackrel(""^(-II))O(l)`

As always...the oxidation reaction represents the FORMAL transfer of electrons between species....