Why isn't nitrous acid a product of nitrite and water?
It should form nitrous acid... If it was $NO_3^{-}$, nitrate ion, then it would presumably form nitric acid $HNO_3$.

Nitrous acid reacts with water to form nitrite and hydronium:

$$\ce{HNO_2 + H_2O -&gt; NO_2^- + H_3O^+} $$

Water is an amphoteric species. Assuming we just have water the nitrite ion, the nitrite ion accepts the hydrogen forming nitrous acid:

$$\ce{NO_2^- + H_2O -&gt; HNO_2 + OH^-} $$

This reaction is interesting as well since nitrous acid will also dissociate again into nitrite ions and water as well:

$$\ce{HNO_2 + H_2O -&gt; NO_2^- + H_3O^+} $$