Sodium nitrite (NaNO2) is a salt that, when dissolved in water, dissociates into sodium ions (Na+) and nitrite ions (NO2-). Nitrite ions are the conjugate base of nitrous acid (HNO2), which is a weak acid. This means that nitrite ions have the ability to accept protons (H+) from water molecules, resulting in the formation of HNO2 and hydroxide ions (OH-).

The equilibrium reaction for this process can be represented as follows:

NO2- + H2O ⇌ HNO2 + OH-

As nitrite ions accept protons, the concentration of hydroxide ions in the solution increases, making the solution basic. Therefore, the solution of sodium nitrite is basic in nature.