Question

In an experiment demonstrating the evolution of oxygen in Hydrilla, sodium bicarbonate is added to water in the experimental setup. What would happen if all the conditions are favourable?
A. Amount of oxygen evolved decreases as carbon dioxide in water is absorbed by sodium bicarbonate.
B. Amount of oxygen evolved increases as the availability of carbon dioxide increases.
C. Amount of oxygen evolved decreases as the availability of carbon dioxide increases.
D. Amount of oxygen evolved increases as carbon dioxide in water is absorbed by sodium bicarbonate.

Answer 1

Hint: The plants produce oxygen as a byproduct of photosynthesis. The photosynthesis is a light dependent process which takes place in the chloroplast of the plant. It prepares food by utilising carbon dioxide.

Complete Answer:
To trap light energy plants use green pigments called chlorophylls. In plants that have chloroplast, it absorbs light energy to make a simple sugar called glucose. The process by which plants use light energy to make glucose is called photosynthesis.

 During this process of sugar production, carbon dioxide combines with water to
form glucose and oxygen is released. Oxygen that is produced in photosynthesis
is given off as a gas. Photosynthesis is occurring rapidly if a lot of oxygen is being given off. If little oxygen is being given off, photosynthesis is occurring slowly.

 The purpose of adding sodium bicarbonate powder to the water increases the amount of carbon dioxide in the water. As the process of photosynthesis requires carbon dioxide, the addition of sodium bicarbonate replenishes the carbon dioxide. This increases the rate of photosynthesis and this oxygen evolved increases.
The amount of trapped light energy and the amount of carbon dioxide available affects the rate of photosynthesis.

So the answer is B. Amount of oxygen evolved increases as the availability of carbon dioxide increases.

Note: From the cut ends of hydrilla twigs more air bubbles will be evolved indicating release of more oxygen. Sodium bicarbonate serves the purpose of carbon dioxide which is required for photosynthesis.