Hydration of alkenes via electrophilic addition

Steps:

• Identify reactants: Ethene (alkene with C=C double bond) and steam (H₂O) with H₂SO₄ catalyst.
• Examine products: Ethanol (CH₃CH₂OH) forms by adding H and OH across the double bond.
• Classify mechanism: H₂SO₄ protonates the double bond, forming a carbocation; water adds, followed by deprotonation.
• Determine reaction type: Addition, as the double bond opens without replacing atoms.

Why A is correct:

• Addition reactions involve breaking a multiple bond and adding atoms/groups across it, matching the formula CH₂=CH₂ + H₂O → CH₃CH₂OH.

Why the others are wrong:

• B: Acid-base involves proton transfer without bond breaking/forming like this; no net acid-base equilibrium here.
• C: Hydrolysis typically cleaves bonds in compounds like esters or salts with water, not adding to unsaturated bonds.
• D: Substitution replaces one atom/group with another, but no group is replaced— the double bond simply adds H₂O.

Final answer: A