Question

The air contaminated by the burning of a candle could not support life in a mouse but support life in plants. This experiment was demonstrated by
A. Priestley
B. Lavoisier
C. Von Mayer
D. None of the above

Answer 1

Hint: The mouse is an animal and it requires oxygen to survive, whereas plants release oxygen. The candle also consumes oxygen to burn and thus devoid the mouse of oxygen to survive. Based on this observation in 1774 a scientist who is considered a discoverer of oxygen performed the given experiment.

Complete answer:
In 1774, an English chemist named Joseph Priestley contributed to the discovery of oxygen by conducting an experiment involving a mouse, candle, and a plant. He also discovered the photosynthesis process in plants. Photosynthesis is a photochemical process that utilizes light energy to produce oxygen as a byproduct. Plants utilize photosynthesis to obtain their food.

Priestly discovered this by keeping a burning candle and a mouse together in a single bell jar. He observed that the candle was extinguished after some time and the mouse died. He then kept a plant along with a mouse and candle in the same jar. He observed that this time both the candle kept burning and the mouse survived. Based on this experiment, Priestley concluded that the air present in the first case of the jar got polluted by a mouse and candle. But in the second case jar, the plant restored the air polluted by mouse and candle. This was possible only due to the occurrence of photosynthesis in the plant. But it was not certain then that what was released by the plant restored the air. Later it was studied that the process was photosynthesis and the component released by the plant was oxygen.
Hence, the correct answer is option A.

Note: Inspired by Priestly, Jan Ingenhousz experimented using the same set and demonstrated that sunlight is also essential for the plant to restore the spoiled air. Jean Senebier then showed that plants take up carbon dioxide and give oxygen during the photosynthesis process. These discoveries together contributed to the discovery of the mechanism of photosynthesis.