Question
Bromothymol blue (BTB) is a pH indicator that is also used to detect carbon dioxide (CO2) in water. BTB is blue when the pH of water is basic and CO2 is low. BTB is yellow when the pH of water is acidic and CO2 is high. BTB is green when the pH of water is neutral.
Students are planning an investigation in which they will place the aquatic plant elodea in a test tube that contains water with a neutral pH of 7 and BRB. They will place a snail in another test tube with neutral water and BTB. The students will then place both elodea and a snail in a third test tube with neutral water and BTB.
Observing color change once the test tubes have been placed under a growth light for several hours will allow the students to answer which TWO questions?
A.
Do elodea and snails require oxygen to survive?
B.
Does elodea produce oxygen during photosynthesis?
C.
Do snails respire faster when placed in a test tube with elodea?
D.
Do snails use the CO2 produced by elodea to produce oxygen?
E.
Does photosynthesis performed by elodea remove CO2 from water?
F.
Does cellular respiration occur at a higher rate than photosynthesis in the test tube with only elodea?
Students are planning an investigation in which they will place the aquatic plant elodea in a test tube that contains water with a neutral pH of 7 and BRB. They will place a snail in another test tube with neutral water and BTB. The students will then place both elodea and a snail in a third test tube with neutral water and BTB.
Observing color change once the test tubes have been placed under a growth light for several hours will allow the students to answer which TWO questions?
A.
Do elodea and snails require oxygen to survive?
B.
Does elodea produce oxygen during photosynthesis?
C.
Do snails respire faster when placed in a test tube with elodea?
D.
Do snails use the CO2 produced by elodea to produce oxygen?
E.
Does photosynthesis performed by elodea remove CO2 from water?
F.
Does cellular respiration occur at a higher rate than photosynthesis in the test tube with only elodea?
Answers
Answered by
GPT-5 mini
Correct answers: E and F.
Reasoning:
- BTB changes color according to dissolved CO2 (yellow = high CO2/acidic; blue = low CO2/basic). A tube with elodea alone that turns blue shows CO2 removal by photosynthesis, so E is answerable.
- In the elodea-only tube the net color (CO2 increase or decrease) reveals whether cellular respiration (which produces CO2) exceeds photosynthesis (which consumes CO2). Thus you can determine if respiration > photosynthesis (F).
- The other options are not supported: the indicator does not measure O2 or survival directly (A, B), cannot isolate snail respiration rate in the mixed tube (C), and snails do not convert CO2 into O2 (D).
Reasoning:
- BTB changes color according to dissolved CO2 (yellow = high CO2/acidic; blue = low CO2/basic). A tube with elodea alone that turns blue shows CO2 removal by photosynthesis, so E is answerable.
- In the elodea-only tube the net color (CO2 increase or decrease) reveals whether cellular respiration (which produces CO2) exceeds photosynthesis (which consumes CO2). Thus you can determine if respiration > photosynthesis (F).
- The other options are not supported: the indicator does not measure O2 or survival directly (A, B), cannot isolate snail respiration rate in the mixed tube (C), and snails do not convert CO2 into O2 (D).