Question

A buffer is used to maintain a constant pH. Explain why the pH of the suspension would increase during photosynthesis in the absence of a buffer. (1)

a) The pH would not increase during photosynthesis.
b) Photosynthesis releases hydrogen ions, causing the pH to increase.
c) Photosynthesis consumes hydrogen ions, causing the pH to increase.
d) The buffer only affects temperature, not pH.

Answer 1

Buffers resist a change in pH after adding an acid or a base by absorbing extra hydrogen ions or hydroxide ions. During photosynthesis, the consumption of hydrogen ions causes the pH of the suspension to increase.

Step-by-step explanation:

Buffers are solutions that resist a change in pH after adding an acid or a base. Buffers contain a weak acid (HA) and its conjugate weak base (A). When excess acid or base is added to a solution, the buffer absorbs the extra hydrogen ions or hydroxide ions, preventing a significant change in pH.

In the case of photosynthesis, carbon dioxide is used up during the process, resulting in a decrease in the concentration of hydrogen ions (H+) in the suspension. When the concentration of hydrogen ions decreases, the pH of the suspension increases, becoming more basic. Therefore, the correct answer is option c) Photosynthesis consumes hydrogen ions, causing the pH to increase.