O Levels Chemistry (5070)•5070/12/M/J/21
Explanation
Roles of V₂O₅ and H₂O in contact process
Steps:
- Contact process oxidizes SO₂ to SO₃ using air over a catalyst.
- V₂O₅ acts as the catalyst to speed up SO₂ + ½O₂ → SO₃ without being consumed.
- SO₃ gas is absorbed in concentrated H₂SO₄ to form oleum.
- Water dilutes oleum to produce H₂SO₄, serving as a solvent in the final step.
Why A is correct:
- V₂O₅ is defined as a catalyst in the exothermic equilibrium reaction, while water dissolves and hydrates the product in the absorption stage per the process description.
Why the others are wrong:
- B: Water directly reacts in SO₃ + H₂O → H₂SO₄ but is not solely a reactant; it's used as solvent for dilution.
- C: V₂O₅ is not consumed as a reactant; it regenerates during catalysis.
- D: Neither is primarily a reactant; V₂O₅ catalyzes, and water solvates.
Final answer: A
Topic: Preparation of salts
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