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200 cm3 of air was passed over heated copper in a syringe several times to produce ...

200 cm3 of air was passed over heated copper in a syringe several times to produce copper (II) oxide.
When cooled, the final volume of air recorded was 158cm3. Estimate the percentage of oxygen in the air?
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  • A 31%
  • B 27%
  • C 21%
  • D 19%
Correct Answer: Option C
Explanation:
Volume of O2 used = 200 - 158 = 42 cm3
% of O2 = (42)/(200) x 100% = 21%

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