Question

The space above the mercury is filled with

• A. Carbon dioxide
• B. NaOH
• C. NO${}_2$
• D. None of the above

Answer 1

The correct option is A Carbon dioxide

This experiment will illustrate anaerobic respiration. Fill a test tube with mercury and invent it over a petri dish containing mercury. Introduce some germinating seeds into the test tube. The seeds will immediately rise to top. Leave the set up for about a day. It is noted that the mercury level in the tube falls and the space above the mercury is filled with a gas. Insert some crystals of caustic potash into the top of the tube. The gas will be quickly absorbed by KOH and the level of mercury rises to the top. Since, KOH absorbs carbon dioxide it is evident that the gas is CO${}_2$. The germinating seeds did not get O${}_2$, so they are exhibiting anaerobic respiration.

Therefore, the correct answer is option D.