JAMB Chemistry 1997 Question 13

Question 13

Air

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 158 cm³. Estimate the percentage of oxygen in the air

A.31%
B.27%
C.21%
D.19%

Show the answer and explanation

Answer: C (21%)

Explanation

The copper removes the oxygen, so oxygen = 200 − 158 = 42 cm³. 42/200 × 100 = 21%.