When hydrogen burns, what is oxygen's role?

1 Answer
Feb 11, 2016

Oxygen acts as the #"oxidant"#, the acceptor of electrons.


The above definition is a formalism, but it does help us to rationalize reactivity. Oxygen lies on the right of the Periodic Table; its high nuclear charge tends to accept electrons, i.e. becoming reduced, and oxidizing another species:

#H_2(g) + 1/2O_2(g) rarr H_2O(g)#

In the reaction above, the reactants are elemental, and have an oxidation state of #0#. In the products, hydrogen has a formal oxidation state of #+I#, and the oxygen has a formal oxidation state of #-II#. Because of its tendency to accept electrons, #O# commonly has a formal oxidation state of #-II# in its compounds. When we assign oxidation states, we remember that these are formalisms; nevertheless, they give us an idea of electron transfer in the reaction.