Final answer:
In the Brønsted theory, an acid is a substance that donates a proton (H+), and a base is a substance that accepts a proton.
Step-by-step explanation:
In the Brønsted theory, an acid is a substance that donates a proton (H+), and a base is a substance that accepts a proton. Let's classify each reactant and product in the given reaction:
Reactant: HCl
Acid or Base: Acid (donates a proton)
Reactant: H2O
Acid or Base: Base (accepts a proton)
Product: Cl-
Acid or Base: Base (accepts a proton)
Product: H3O+
Acid or Base: Acid (donates a proton)