Oxidizing agent, reducing agent, acid or base In concrete reactions, how can you define whether Ammonia reacts as an oxidizing agent, reducing agent, an acid or a base? I'm confused because in the examples given it's not an acid/ base when an $\ce {H+}$ is donated/ accepted.

$$\ce {2NH3 + 3Cl2 -&gt; N2 + 6HCl}$$ (oxidizing agent)

$$\ce {Na + NH3 -&gt; NaNH2 + \frac{1}{2}H2}$$ (reducing agent)

$$\ce{NH3 + H2O + CO2 -&gt; NH4HCO3}$$ (base)

$$\ce{NH3 + LiCH3 -&gt; LiNH2 + CH4}$$ (acid)
The use of the terms "oxidizing agent" and "reducing agent" in this example apparently refer to the overall reaction. Ammonia certainly can act as an acid in the process of reacting with sodium metal, and as a (Lewis) base during the reaction with chlorine. However, the net effect of the reaction is a reduction or oxidation, rather than a simple proton transfer.