Why isn't nitrous acid a product of nitrite and water? Question
  Predict the products of the following acid-base reactions, and predict whether the equilibrium lies to the left or to the right of the equations
  $$\ce{NO2- + H2O -&gt; ?}$$


I thought it would be $\ce{NO2- + H2O -&gt; HNO2 + OH-}$, but my textbook says that the correct products are $\ce{HNO3}$ and $\ce{OH-}$. What am I doing wrong here? The answer that they give doesn't even seem to balance.
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:

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