Question

Who demonstrated that green plants purify the foul air produced by breathing animals and burning candles?
A. Priestley
B. Ingenhousz
C. Sachs
D. Engelmann

Answer 1

Hint: He was a scientist who performed an experiment using a mouse, candle, and a plant. He took some years to understand what the plant is releasing some substance. Hence the rat was alive and the candle remained burning.

Complete Answer:
- In this specific question, we need to understand that photosynthesis is a mechanism in which the light energy received by the plants is turned into chemical energy resulting in the formation of Oxygen.
- Numerous experiments were conducted by many scientists to understand the process of photosynthesis. In this process, plants require water, carbon dioxide, and organelles like chloroplast. In the presence of sunlight, these raw materials are used to make carbohydrates as food.

 One such experiment was conducted by an eminent scientist Joseph Priestley. In the year 1770, Joseph Priestley being very interested in natural sciences performed a historic experiment. He lit a candle and put it in a closed jar and found the candle soon got off.
- Similarly, a mouse died when kept in the same closed jar. But when he added a plant in that same jar, he observed that the mouse survived along with the lighted candle. He drew the inference that the air in the jar got full of carbon dioxide by exhalation of the mouse and it got restored through plants.
- Also, he concluded that foul air formed due to the burning of candles and respiration in the mouse was getting converted to pure air by plants. Therefore, it showed that the plants give the air its freshness back.
- Interestingly, 4 years later, he discovered oxygen. The name oxygen was given by Lavoisier. He also found that animals and humans ‘consume air’ i.e. Oxygen and that plants take carbon dioxide and give oxygen.

Hence, the correct option is A.

Note: Joseph Priestley and Carl Wilhelm Scheele both worked separately and discovered oxygen. Out of them, Priestley was the one who was given recognition for the discovery.