O Levels Chemistry (5070)•5070/11/M/J/22
Explanation
Oxygen Consumption in Candle Burning Experiment
Steps:
- Candle flame reacts with oxygen from air inside the container to produce CO2 and H2O.
- Oxygen (about 21% of initial air volume) is consumed, reducing total gas volume.
- Atmospheric pressure pushes water up to equalize pressure inside the container.
- Final water level rises by approximately 21% of initial air volume above the candle.
Why C is correct:
- Diagram C shows water level rising by roughly one-fifth of the air space, matching the oxygen volume fraction per the composition of air.
Why the others are wrong:
- A shows no water level change, ignoring gas volume reduction.
- B shows water fully filling the container, overestimating oxygen consumption.
- D shows minimal rise, underestimating the oxygen proportion in air.
Final answer: C
Topic: Redox
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