Tennessee Wastewater Operator Practice Exam

How many pounds of oxygen are needed to convert 1.00 lb of ammonia into nitrate?

1. 3.57

2. 4.00

3. 4.57

4. 5.00

The correct answer is: 4.57

To determine how many pounds of oxygen are needed to convert 1 pound of ammonia (NH₃) into nitrate (NO₃⁻), we can refer to the biochemical process known as nitrification, which occurs in two steps involving specific bacteria. In the first step, ammonia is oxidized to nitrite (NO₂⁻), and this reaction requires oxygen. In the second step, nitrite is further oxidized to nitrate, which also consumes oxygen. The overall stoichiometry for the full conversion from ammonia to nitrate can be broken down as follows: 1. The conversion of ammonia to nitrite can be summarized by the reaction: NH₃ + 1.5 O₂ → NO₂⁻ + H₂O 2. The conversion of nitrite to nitrate can be represented by: NO₂⁻ + 0.5 O₂ → NO₃⁻ When we combine these two reactions, the total reaction for converting ammonia to nitrate can be summarized as: NH₃ + 2 O₂ → NO₃⁻ + H₂O This indicates that for every mole of ammonia that is converted to nitrate, two moles of oxygen are required. Since the molecular