Question

When CO2 combines with water it forms carbonic acid. How does this explain the phenol red result?

Answer 1

Answer:

Detail is given below.

Explanation:

First of all we will understand the pH.

pH:

pH is the negative log of hydrogen ion concentration.

pH = -[logH⁺]

It means when the  ions concentration increases pH will be low and when H⁺ concentration ions decreases pH will be greater. The pH range is 0-14.

If the pH is 7 the solution is neutral, if it is less than 7 the solution will be acidic and above 7 the solution is basic.

when CO₂ is added with water carbonic acid is formed and yield H⁺ ions which decreases the pH thus its color changes from red to yellow just like phenolic indicator. When phenol red is added into the acidic solution the color changes from red to yellow.

and when carbon dioxide is take off from photosynthesis process it means H⁺ ions are going to be decreased thus color changes from yellow to red.