O Levels Chemistry (5070)•5070/11/O/N/19
Explanation
Collecting dry SO2 using downward delivery
Steps:
- React Na2SO3 with HCl to produce SO2 gas: Na2SO3 + 2HCl → 2NaCl + H2O + SO2.
- SO2 is denser than air (density 2.86 g/L vs. air 1.29 g/L), so collect by downward delivery.
- Reaction produces wet SO2; dry it using concentrated H2SO4 in a drying tube, as SO2 is soluble in water but not in H2SO4.
- Apparatus must include generating flask, drying tube, and inverted collection jars filled with water for displacement.
Why C is correct:
- C shows reaction flask connected to H2SO4 drying tube and downward delivery setup, matching SO2's density and drying needs per gas collection principles.
Why the others are wrong:
- A uses upward delivery, unsuitable for denser-than-air SO2.
- B lacks drying agent, yielding wet SO2 sample.
- D uses bubbling through water, which dissolves soluble SO2.
Final answer: C
Topic: Experimental design
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