reduction of carbon

Forinorganic reactions of carbon, the half ionic equation can be written as :
C(s) + 2H2O(l) → CO2(g) + 4H⁺(aq)

For example, carbon acts as a reducing agent to react hot concentrated nitricacid, and the two half ionic equations are :
C(s) + 2H2O(l) → CO2(g) + 4H⁺(aq) + 4e⁻ ...... (*)
2H⁺(aq)+ NO­3­⁻(aq) + e⁻ → H2O(l) + NO2­(g) ......(#)

4(*) + (#), and cancel 2H2O(l) and 4H⁺(aq) on the both sides. The overall ionicequation is :
C(s) + 4H⁺(aq)+ 4NO­3­⁻(aq)→ CO2(g)+ 2H2O(l) + 4NO2(g)

Hence, the overall full equation is :
C(s) + 4HNO­3(aq)→ CO2(g) + 2H2O(l) + 4NO2(g)

2014-10-02 19:22:03 補充：
It should be "(*) + 4(#)" instead of "4(*) + (#)".

Note that when carbon acts as a reducing agent, it actually undergoes OXIDATION. It is oxidized to give carbon dioxide.