You are absolutely correct! The solution at the equivalence point of an HCl titration with Na₂CO₃ is indeed slightly acidic, and here's why:

The Reaction:

The reaction between HCl and Na₂CO₃ is:

2HCl(aq) + Na₂CO₃(aq) → 2NaCl(aq) + H₂O(l) + CO₂(g)

The Role of Bicarbonate:

At the equivalence point, all the Na₂CO₃ has reacted, and you're left with a solution containing NaCl and the products of the reaction between H₂O and CO₂. This reaction forms carbonic acid (H₂CO₃):

CO₂(g) + H₂O(l) ⇌ H₂CO₃(aq)

Carbonic acid is a weak acid. It partially dissociates into bicarbonate (HCO₃⁻) and hydrogen ions (H⁺):

H₂CO₃(aq) ⇌ H⁺(aq) + HCO₃⁻(aq)

The Slightly Acidic Nature:

Even though the reaction initially neutralizes all the HCl, the presence of the bicarbonate ion, HCO₃⁻, leads to a slight acidity. Bicarbonate can act as a weak acid, donating a proton to water:

HCO₃⁻(aq) + H₂O(l) ⇌ H₃O⁺(aq) + CO₃²⁻(aq)

This small amount of H₃O⁺ generated from bicarbonate dissociation makes the solution slightly acidic.

Summary:

While the reaction stoichiometry suggests a neutral solution at the equivalence point, the formation of carbonic acid and its subsequent weak acid dissociation leads to a slight excess of H⁺ ions, resulting in a slightly acidic solution.