Sodium bisulfite (NaHSO₃) is acidic, and its pH is typically around 4.5-5.5.

Here's why:

* Hydrolysis: When sodium bisulfite dissolves in water, it undergoes hydrolysis, forming bisulfite ions (HSO₃⁻) and sodium ions (Na⁺). The bisulfite ions can donate a proton (H⁺) to water, making the solution acidic:

```

HSO₃⁻ + H₂O ⇌ SO₃²⁻ + H₃O⁺

```

* Equilibrium: The equilibrium lies to the right, meaning more bisulfite ions donate protons, increasing the concentration of hydronium ions (H₃O⁺) and lowering the pH.

Important Notes:

* Concentration: The exact pH of a sodium bisulfite solution depends on its concentration. A more concentrated solution will be more acidic.

* Temperature: Temperature also affects pH. A higher temperature will favor the production of H₃O⁺, making the solution more acidic.

Let me know if you have any other questions!