Question

I am putting together a (fake) proposal for a process that would convert ammonia in cow manure into elemental nitrogen. The first step includes the conversion of that ammonia into ammonium so that it can be used by bacteria in a later step. I know that this specific reaction favors the reactants, so I am looking to find the right combination of methods to push equilibrium towards the products. I used le chatelier's principle and noted an excess of H20 already, but I have a hunch that wouldn't be enough to sway the equilibrium as much as I want. I know that reducing pH would also favor the products. My concern is that there would be a reaction with the desired ammonium and any acid (or their conjugate bases) added to the solution. Would a common strong acid (HCl, H2SO4, etc) would be appropriate for this scenario, or is there another method of removing OH- from the solution that could work?

Answer 1

To convert ammonia to ammonium, adding acid is one approach but carries the risk of side reactions. Instead, following the principle used in the Haber-Bosch process, removing OH- ions or NH3 from the system could also shift the equilibrium favorably towards NH4+ without adding acids. Adjusting temperature, pressure, and using catalysts are also viable methods.

Step-by-step explanation:

The student is considering a proposal for converting ammonia (NH3) from cow manure into nitrogen gas (N2) using a bacterial process. To push the equilibrium towards the production of ammonium (NH4+), the student suggests using strong acids like HCl or H2SO4 to lower the pH, which would favor the formation of NH4+. However, they are concerned about potential reactions between the added acids and the desired ammonium product.

To influence the chemical equilibrium without the downside of additional reactions, the student could consider other methods such as the removal of a substance from the system, as demonstrated in the Haber-Bosch process. In this industrial process, NH3 is continually removed, which drives the reaction towards product formation. Applying this concept, removing some of the OH- ions or NH3 itself from the reaction could shift the equilibrium favorably towards NH4+ formation without necessarily adding acids. Additionally, adjusting other conditions like temperature and pressure, as well as utilizing catalysts, can also affect the equilibrium to favor the desired direction.