Photosynthesis Question 10
10. Suppose an aquatic plant is placed in a test tube containing distilled water and the tube is stoppered. The tube is left outdoors for 24 hours and the $pH$ value of the water is then measured at regular intervals. Which of the following is the most probable result? [1997]
(a) The $pH$ value is lowest just before sunrise
(b) The $pH$ value is highest just before sunrise
(c) The $pH$ value is lowest at noon
(d) The $pH$ value is lowest just before sunset.
Show Answer
Answer : a
Hints & Solution
(a) After sunrise, photosynthesis is carried out using $CO_2$. Hence concentration of $CO_2$ decreases increasing $pH$.
