JAMB - Chemistry (1997 - No. 11)
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?
When cooled, the final volume of air recorded was 158cm3. Estimate the percentage of oxygen in the air?
31%
27%
21%
19%
Explication
Volume of O2 used = 200 - 158 = 42 cm3
% of O2 = (42)/(200) x 100% = 21%
% of O2 = (42)/(200) x 100% = 21%