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 other 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

The correct option is B Amount of oxygen evolved increases as the availability of carbon dioxide increases.

Hydrilla is a green aquatic plant that carries out photosynthesis using carbon dioxide, water and sunlight to produce organic compounds and oxygen. Sodium bicarbonate is dissociated into sodium and bicarbonate ions, bicarbonate ions ($HC{O}_3$-) react with water to produce carbonic acid and $O{H}^{-}$. The carbonic acid ($H_{2}C{O}_3$) is readily decomposed into water and carbon dioxide. Since carbon dioxide is one of the initial substances for photosynthesis, increased availability of this gas increases the rate of photosynthesis as well as the release of oxygen provided all other factors are favourable. Thus, the correct answer is option B.