Biology 0610 · IGCSE · Gas exchange in humans

Gas exchange in humans — practice question

A sample of expired air is gathered in a gas jar. A second gas jar is filled with normal atmospheric air. A lighted candle is then put into each gas jar, as shown. The time for each flame to go out is recorded. As the candles burn, they use the oxygen present in the jar. The table gives the results of this experiment. What explains the difference in the results for jars X and Y?

  • AJar X contains atmospheric air which has more carbon dioxide.
  • BJar X contains expired air which has more carbon dioxide.
  • CJar Y contains atmospheric air which has less oxygen.
  • DJar Y contains expired air which has less oxygen.

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