Chlorine gas (Cl₂) itself is not acidic or alkaline. It's a non-polar covalent molecule, meaning it doesn't readily form ions in water and therefore doesn't exhibit acidic or basic properties.

However, when chlorine gas dissolves in water, it undergoes a reaction to form hypochlorous acid (HClO) and hydrochloric acid (HCl):

Cl₂ + H₂O ⇌ HClO + HCl

Hypochlorous acid (HClO) is a weak acid and contributes to the acidic nature of the solution. This is why chlorine solutions are used as disinfectants and bleaches, as the hypochlorous acid is a powerful oxidizing agent.

Hydrochloric acid (HCl) is a strong acid, but it is produced in smaller amounts compared to hypochlorous acid.

Therefore, while chlorine gas itself is neither acidic nor alkaline, its aqueous solutions exhibit acidic properties due to the formation of hypochlorous acid.