Showing that air contains about one-fifth oxygen
1 mark · NormalWhich statement best describes how the percentage of oxygen in air can be found using an experiment with wet iron filings?
Show answer
Correct option: Measure the decrease in volume of gas in the apparatus.
Common mistakes: Choosing volume increase or temperature measurement
Show mark scheme and worked solution
Marking points
B1 · 1 mark · Correct option chosen: Measure the decrease in volume of gas in the apparatus.
Worked solution
The correct answer is: Measure the decrease in volume of gas in the apparatus. As iron rusts, it uses up oxygen so the volume of gas falls.