Answer the entirety of the question: a, b, and c. Large blooms of algae result f
ID: 506687 • Letter: A
Question
Answer the entirety of the question: a, b, and c.
Large blooms of algae result from high nutrient loading in rivers and lakes, for example, as a result of runoff of fertilizers from agricultural fields. When the algae die, they biodegrade and consume oxygen. The amount of oxygen consumed is BOD. If the level of oxygen dissolved in water becomes too low, fish become stressed and susceptible to viral or bacterial infections. In severe cases, fish die. A simplified empirical formula for algae is C_6 H_15 O_6 N. (Micronutrients are not included because they are present in much smaller quantities than C, H, O, and N). a. Write a balanced chemical reaction for the degradation (oxidation) of 1 mol of algal cells to CO_2, H_2 O, and NH_3. b. Calculate the theoretical BOD of algae (g BOD/g algae). The oxidation is not truly "complete" as written in part a) since nitrogen is still present in a reduced state (NH_3). However, ammonia is not oxidized as quickly as the carbon and hydrogen species present, and its oxidation is typically not counted as part of the BOD. Instead, the oxygen required for nitrification is considered to be the "chemical oxygen demand" (COD). c. Do algae have a higher or lower BOD than glucose (on a weight basis)?Explanation / Answer
a. C6H15O6N + 6O2 ---------> 6 CO2 + 6 H2O + NH3
b. 1 mol algae require = 6 mole O2
197 g algae require = 6 x32 /197 = 0.97 g [molar mass of algae = 197 and molar mass of O2 = 32]
Theoretical BOD = 0.97g BOD/g algae
c. molar mass of glucose = 180
Theoretical BOD for glucose = 6 x 32/180 = 1.07 g [1 mole gluocse require 6 mole O2 for complete oxidation]
So, algae have a lowet BOD than glucose.