Question

Read the following description of Tube #2:

Tube #2 contains:

Bromothymol blue (BTB)
Carbon dioxide
Exposed to light
Elodea present
Initially yellow-green in color
After 24 hours, Tube #2 is now blue in color. In 1 sentence explain why.

Answer 1

Tube #2 turned blue after 24 hours because the Elodea, a photosynthetic plant, consumed carbon dioxide during photosynthesis, reducing the acidity of the solution and resulting in a color change from yellow-green to blue with the bromothymol blue indicator.