Here's why:

* Na₂C₂O₄ is the sodium salt of oxalic acid (H₂C₂O₄). Oxalic acid is a weak diprotic acid.

* Salts are formed from the reaction of an acid and a base. In this case, the sodium (Na+) ions come from a strong base like NaOH, and the oxalate (C₂O₄²⁻) ions come from the weak acid H₂C₂O₄.

* The salt itself doesn't act as an acid or base. However, when dissolved in water, it can hydrolyze, meaning the oxalate ions can react with water to produce a small amount of hydroxide ions (OH⁻), making the solution slightly basic.

In summary: Na₂C₂O₄ is a salt formed from a strong base and a weak acid. While it doesn't act as a strong acid or base itself, it can exhibit slightly basic properties in solution due to hydrolysis.