Astudent poured a solution of bromothymol blue (bmb) into three test tubes. (bmb turns yellow in the presence of co2.) then he placed an aquatic plant in two of the test tubes, as shown in the diagram (you will see the diagram when you are taking the test). he placed a stopper on each test tube and placed them all in the dark for two days. predict what change of color, if any, would occur in each of the test tubes. explain your answer. (2 points extra credit): describe what color change would occur in each tube, if any, if the experiment were done in the light. explain your answer.

Bromothymol blue is an indicator dye that turns yellow in presence of an acid. It remains blue if the pH of the given solution is greater than 7.6 and yellow when the pH is less than 6. The yellow coloration is due to the formation of carbonic acid in the from the carbon dioxide present in the solution.

When aquatic plants are added to two test tubes containing bromothymol blue, stoppered and kept in dark for two days, no color change is observed. It is because the carbon dioxide present is utilized in the process of photosynthesis by plants. If the experiment is conducted in presence if the light, the color of bromothymol blue would be yellow due to the presence of carbon dioxide.