Sodium hydrogen phosphate (Na₂HPO₄) reacts with water in a process called hydrolysis. This reaction results in the formation of a slightly basic solution.

Here's a breakdown of the reaction:

* The hydrogen phosphate ion (HPO₄²⁻) acts as a weak base. It accepts a proton (H⁺) from water, forming the dihydrogen phosphate ion (H₂PO₄⁻) and hydroxide ions (OH⁻).

* The equation for the hydrolysis reaction is:

HPO₄²⁻(aq) + H₂O(l) ⇌ H₂PO₄⁻(aq) + OH⁻(aq)

* The presence of hydroxide ions (OH⁻) in the solution makes it slightly basic.

Important Notes:

* The reaction is an equilibrium reaction, meaning it proceeds in both directions.

* The extent of hydrolysis (and the resulting pH) depends on the concentration of sodium hydrogen phosphate.

* Sodium hydrogen phosphate is a common buffer, meaning it helps to resist changes in pH.

In summary, the reaction of sodium hydrogen phosphate and water results in a slightly basic solution due to the hydrolysis of the hydrogen phosphate ion.