For each of the following factors, indicate whether the pH increases or decreases and explain why the

For each of the following factors, indicate whether the pH increases or decreases and explain why the factor may cause variation in pH in streams or water bodies (read background pgs. 4 and 5):

a) Photosynthesis (6CO2 6H2O > C6H12O6 6O2): pH increases / decreases

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  1. a) Photosynthesis ( 6CO₂+ 6H₂0 > C₆H₁₂0₆ + 60₂): pH increases

    b) Respiration ( C₆H₁₂0₆+ 0₂ > CO₂  + H₂O + ATP): pH decreases

    c) Contamination with substance that releases hydroxyl/hydroxide ions: pH increases

    d) Contamination with substance that releases hydrogen ions: pH decreases

    Explanation:

    (1) More the acidic environment, lesser will be the pH.

    (2) More will be the basic environment, more will be the pH.

    a) Photosynthesis ( 6CO₂+ 6H₂0 > C₆H₁₂0₆ + 60₂): pH increases:

    During photosynthesis, carbon dioxide (CO₂) is utilized to produce oxygen (O₂). CO₂ is responsible for making the environment acidic because it has tendency to combine with water (H₂O) so as form form carbonic acid (H₂CO₃). The reaction is mentioned as under:  

                      CO₂ + H₂O  ⇄  H₂CO₃

    But, during photosynthesis carbon is being used as a result of which it's concentration is decreasing in the environment. Less CO₂ means less acidic environment leading to an increase in pH.

    b) Respiration ( C₆H₁₂0₆+ 0₂ > CO₂  + H₂O + ATP): pH decreases:

    During respiration, carbon dioxide (CO₂) is being produced as a result of which environment will become more acidic leading to a decrease in pH.

    c) Contamination with substance that releases hydroxyl/hydroxide ions: pH increases:

    When hydroxyl/hydroxide ions [OH⁻] in the environment increase, it adds to the basicity and decreases acidity. An increase in basic environment leads to an increase in pH.

    d) Contamination with substance that releases hydrogen ions: pH decreases:

    When hydrogen ions [H⁺] in the environment increase, it adds to the acidity and decreases basicity. An increase in acidic environment leads to a decrease in pH.

  2. Photosynthesis can increase the pH level of the water and the reason is because it removes carbon dioxide that is present in the water.

    Explanation:

    Photosynthesis is a chemical process/cycle that is executed by plants by consuming carbon dioxide and releasing oxygen into the air or water.

    The photosynthesis can cause the pH level of the water to rise because of the removal of carbon dioxide from the environment.

    I hope this answer helps.

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