In the reaction:
HCl + H2O → Cl⁻ + H3O⁺
HCl donates a proton (H⁺) to H2O. In this context:
- HCl acts as an acid (specifically, it donates a proton).
- H2O acts as a base (specifically, it accepts a proton).
After the reaction:
- Cl⁻ is the conjugate base of HCl (the species that remains after the acid donates a proton).
- H3O⁺ is the conjugate acid that forms from H2O after it accepts a proton.
Therefore, the correct statement about the reaction is:
HCl is an acid, and Cl⁻ is its conjugate base.