Question

Does oxidation cause an increase or decrease in mass?

Answer 1

Well formally yes........

Explanation:

Because oxidation represents the formal LOSS of electrons.....

`Na(s) rarr Na^(+) +e^(-)`

And since electrons have definite (admittedly negligible) mass, this is a formal mass loss.

Of course for every oxidation there is a corresponding reduction , so certainly mass is conserved in the overall redox equation.

`H_2O +e^(-) rarr 1/2H_2(g) + HO^-`

and the overall reaction is........

`Na(s)+ H_2O(l) rarr NaOH(aq) + 1/2H_2(g)`