Will monosodium dihydrogen phosphate react as base or acid in water?

Will $\ce{NaH2PO4}$ react as as an acid or a base if you make it react with water?


I got stuck here. I can figure out the reaction:


$$\ce{NaH2PO4 + H2O -> Na^+ + H2PO4^- + H2O}$$


But when I look $\ce{H2PO4^{-}}$ up, it says that it can both be an acid and a base. 
Any ideas? 




Monosodium dihydrogen phosphate, $\ce{H2PO4^-}$, is an amphoteric species and it will act as both an acid and a base. 
These are the related chemical equations:


\begin{align}
 \ce{H2PO4- + H2O &<=> HPO4^2- + H3O+} & \mathrm{p}K\_\mathrm{a} &= 7.21\\
 \ce{H2PO4- + H2O &<=> H3PO4 + OH-} & \mathrm{p}K\_\mathrm{b} &= 11.88
\end{align}


As an example, $\pu{0.1 M}$ solution of such a salt will have a pH of about $4.7$.
In other words, the acidic behaviour dominates over the alkaline one. This is due to the value of $\mathrm{p}K\_\mathrm{a}=7.21$ (related to the acidic behaviour) compared to the $\mathrm{p}K\_\mathrm{b}=11.88$ (related to the alkaline behaviour).


 5