WAEC Chemistry 2025 Objective — Question 1
Question 1 of 50 from the West African Examinations Council (WAEC) Chemistry 2025 Objective paper, with the correct answer and a full explanation.
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Which of the following pairs of gases cannot be collected by downward delivery of air?
- A. SO2 and NH3
- B. CO and N2
- C. Cl2 and N2
- D. SO2 and N2Correct
Explanation
Only gases denser than air are collected by downward delivery (upward displacement of air). A gas is considered denser than air if its relative molecular mass is greater than 28.8. SO2=64, NH3=17, CO=28, N2=28, Cl2=71. SO2 and Cl2 can be collected this way, but NH3, CO and N2 cannot (they are less dense than or about the same as air), so SO2 and N2 is the pair that cannot both be collected by downward delivery.
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