EVERYDAY SCIENCE

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SCIENCE

RESPIRATION

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Two test tubes were filled with a solution of bromthymol blue. A student exhaled through a straw into each tube, and the bromthymol blue turned yellow. An aquatic green plant was placed into each tube, and the tubes were corked. One tube was placed in the dark, and one was placed in direct sunlight. The yellow solution in the tube in sunlight turned blue, while the one in the dark remained yellow. Which statement best explains why the solution in the tube placed in sunlight returned to a blue color?
A
Oxygen was produced by photosynthesis.
B
Carbon dioxide was removed by photosynthesis.
C
Carbon dioxide was produced by respiration.
D
Oxygen was removed by respiration.
Explanation: 

Detailed explanation-1: -As a result, an acid-base indicator such as bromothymol blue (btb) can be used to indicate the presence of carbon dioxide. In this lab, you will use bromothymol blue as an indicator to show how much CO2 is left in test tubes containing plants exposed to light.

Detailed explanation-2: -Expose the cylinder to sunlight for 20 minutes. [The yellow solution will change back to blue because the plant will utilize the carbon dioxide, making the solution less acidic, converting the color back to blue. ]

Detailed explanation-3: -Bromothymol blue (BMB) is an indicator dye that turns yellow in the presence of acid. When carbon dioxide is added to the solution, it creates carbonic acid, lowering the pH of the solution. BMB is blue when the pH is greater than 7.6, green when the pH is between 6-7.6, and yellow when the pH is less than 6.

Detailed explanation-4: -Carbon dioxide production can be measured by breathing through a straw into a solution of bromothymol blue (BTB). BTB is an acid indicator; when it reacts with acid it turns from blue to yellow.

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