Catalyst in Contact Process for Sulfuric Acid

Steps:

• Identify steps: P burns sulfur to SO2 (no catalyst); Q oxidizes SO2 to SO3 (V2O5 catalyst); R absorbs SO3 in H2SO4 to form oleum (no catalyst).
• Recall Contact Process: Catalyst accelerates SO2 to SO3 conversion without being consumed.
• Confirm usage: Only Q requires catalyst for efficient reaction at 450°C.
• Eliminate others: P and R are non-catalytic.

Why C is correct:

• In the Contact Process, vanadium(V) oxide (V2O5) catalyzes 2SO2(g) + O2(g) ⇌ 2SO3(g), matching step Q.

Why the others are wrong:

• A: Includes P and R, which lack catalysts.
• B: Adds R, but absorption step uses no catalyst.
• D: Omits Q, the sole catalytic step.

Final answer: C