Question

The diagram given below represents an experiment to prove the importance of a factor in photosynthesis. Answer the questions that follow:

1. Which factor is being studied here?
2. What is the purpose of keeping KOH in the flask?
3. Explain the term photosynthesis.
4. What will you observe when the leaf is tested for starch?
5. Write awell-balanced chemicalequation for the process of photosynthesis.

Answer 1

1. Carbon dioxide (CO₂) is the factor being studied to prove that it is essential for photosynthesis (Moll's half-leaf experiment).
2. Potassium hydroxide (KOH) is used to absorb all the carbon dioxide (CO₂) gas inside the flask, ensuring that the half of the leaf inside receives no CO₂.
3. Photosynthesis is the process by which green plant cells manufacture glucose from simple inorganic raw materials like carbon dioxide and water using solar energy trapped by chlorophyll, releasing oxygen and water as by-products.
4. • The part of the leaf that was outside the bottle turns blue-black, which confirms that starch is present because this part received carbon dioxide (CO₂) from the outside air.
   • The part of the leaf that was inside the bottle turns brownish or pale yellow, which confirms that no starch is formed because carbon dioxide (CO₂) was missing inside the bottle.
5. \[ 6\mathrm{CO_2} + 12\mathrm{H_2O} \xrightarrow[\ \text{Chlorophyll}\ ]{\ \text{Sunlight}\ } \mathrm{C_6H_{12}O_6} + 6\mathrm{H_2O} + 6\mathrm{O_2} \uparrow \]