Question

How do you classify this reaction? `8HNO_3 (aq) + 3 Cu (s) + O_2 (g) -> 3Cu(NO_3)_2 (aq) + 4H_2O + 2NO_2 (g)`

Answer 1

This is CLEARLY a redox process, which we represent by invoking electrons as virtual particles........I do not think dioxygen is a reasonable reactant.

Explanation:

Copper is oxidized up to cupric ion, `Cu^(2+)`:

`Cu(s) rarr Cu^(2+) + 2e^(-)` `(i)`

Nitrate ion `N(V)` is REDUCED to `NO_2(g)`, `N(IV)`:

`NO_3^(-) +2H^(+) +e ^(-) rarr NO_2 +H_2O` `(ii)`

We take `(i) + 2xx(ii)` to give......

`Cu(s) + 2NO_3^(-) +4H^(+) +cancel(2e ^(-)) rarr Cu^(2+) + cancel(2e^(-))+2NO_2 +2H_2O`

And cancel out the common reagents......

`Cu + 2NO_3^(-) +4H^(+) rarr Cu^(2+) +2NO_2 +2H_2O`