Question

carbon dioxide (co₂) is consumed during photosynthesis and is produced during cellular respiration.
photosynthesis and cellular respiration can be summarized by equations 1 and 2, respectively:

1. 6co₂ + 6h₂o + light energy → c₆h₁₂o₆ + 6o₂
2. c₆h₁₂o₆ + 6o₂ → 6co₂ + 6h₂o + energy

when co₂ dissolves in an aqueous solution, an acid is formed. thus, the ph of an aqueous solution
is affected by the concentration of co₂ dissolved in the solution. a student performed an experiment
to determine how the ph of an aqueous solution is affected by the addition to the solution of an
organism that is undergoing both photosynthesis and cellular
respiration, an organism that is undergoing cellular respiration but
not photosynthesis, or both such organisms.
experiment
the student prepared a sterile aqueous solution containing
bromothymol blue (btb). a btb
solution can be yellow, green, or
blue in color, depending on its
ph (see table 1). the students
solution was green.
the student placed 10 ml of
the solution into each of 8 sterile
tubes (tubes 1 - 8). then she
added a piece of elodea (a
water plant), a snail, or both to
each of tubes 3 - 8, placed a cap
on each of the tubes 1 - 8, and
incubated all 8 tubes at 25°c for
24 hr (dark treatment) or
constant light for 24 hr (light
treatment). table 2 lists, for
each tube, the organism(s)
present (if either), whether the
dark or the light treatment was
received, and the color of the
solution at the end of the 24 hr incubation.

1. at the end of the 24 hr incubation, the ph of the solution in tube 1 was closest to which of the following

values?
a. 2.0 b. 4.0 c. 7.0 d. 10.0
support with evidence:

Explanation:

Step1: Analyze Table 1

Table 1 shows the relationship between pH and the color of BTB solution.

Step2: Check Tube 1's color

From Table 2, Tube 1 has a color of Green at the end of 24 - hr incubation.

Step3: Determine pH range

According to Table 1, when the BTB solution is Green, the pH range is \(6.0 - 7.6\).

Answer:

C. 7.0