Final answer:
The reaction SO₃ (g) + H₂O (l) → H₂SO₄ (aq) is a synthesis reaction, where sulfur trioxide and water combine to form sulfuric acid.
Step-by-step explanation:
To classify the given chemical reaction SO₃ (g) + H₂O (l) → H₂SO₄ (aq), we need to look at the reactants and the products. In this reaction, sulfur trioxide (SO₃) and water (H₂O) combine to form sulfuric acid (H₂SO₄). This is a classic example of a synthesis reaction, also known as a composition reaction, where two or more simple substances combine to form a more complex substance.
In there, SO₃ and H₂O are the reactants, and H₂SO₄ is the product. The reaction takes two substances and synthesizes one product, which fits the definition of a synthesis reaction.