Mass of ammonia through nitrate concentration problem

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Discussion Overview

The discussion revolves around calculating the mass of ammonia that would produce a specified concentration of nitrate in an aquifer. Participants explore the relationship between nitrate concentration, volume, and the stoichiometry of the chemical reaction involved in the oxidation of ammonia to nitrate.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant calculates the mass of nitrate based on a concentration of 20 ppm in a volume of ten million liters, arriving at a mass of 2*10^8 mg.
  • Another participant clarifies that the 1:1 ratio refers to moles of nitrogen, not mass, in the reaction between ammonia and oxygen to produce nitrate.
  • A different participant suggests a simpler approach to calculating the mass of nitrate by directly applying the ppm value to the total volume, resulting in a mass of 200 mg, indicating a disagreement with the previous calculation by a factor of 1000.
  • Concerns are raised about the use of ppm as a unit for reporting nitrate concentrations, with one participant questioning the practicality of weighing out 'nitrate' as a substance.
  • Another participant counters that using proxies like nitrate is common in reporting, suggesting that it is an acceptable practice.

Areas of Agreement / Disagreement

Participants express differing views on the calculations and the appropriateness of using ppm as a unit for nitrate concentrations. There is no consensus on the correct mass of ammonia or the best approach to the problem.

Contextual Notes

Participants highlight potential confusion regarding the conversion between nitrate mass and ammonium mass, as well as the implications of using ppm in chemical contexts. The discussion remains unresolved regarding the correct interpretation and calculation methods.

Frankenstein19
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Homework Statement


The nitrate concentration in an aquifer is 20 ppm, and its volume is ten million
liters. What mass of ammonia upon oxidation would have produced this mass of
nitrate? [Hint: The moles of nitrogen in reactant and product are identical.]

Homework Equations


Possibly 1mg/L & NH3+O2---->NO3-

The Attempt at a Solution


Since 1mg/L equals 1ppm then I'd get a 2*10^8mg for nitrate mass. And NH3+O2---->NO3- (through aerobic contitions and nitrification, idk if this is applicable >: ) then the 1:1 ratio means there's an equal amount of ammonium?
 
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1:1 in terms of moles, not mass.
 
Frankenstein19 said:

Homework Statement


The nitrate concentration in an aquifer is 20 ppm, and its volume is ten million
liters. What mass of ammonia upon oxidation would have produced this mass of
nitrate? [Hint: The moles of nitrogen in reactant and product are identical.]

Homework Equations


Possibly 1mg/L & NH3+O2---->NO3-

The Attempt at a Solution


Since 1mg/L equals 1ppm then I'd get a 2*10^8mg for nitrate mass. And NH3+O2---->NO3- (through aerobic contitions and nitrification, idk if this is applicable >: ) then the 1:1 ratio means there's an equal amount of ammonium?

Why not be a bit simpler? You have 20 parts per million, then if you have 1 million, 20 parts of it is 20, 20 parts per million of 10 million is 200!

We have a disagreement there by a factor of 1000.

After you are sure about that, you have to convert the nitrate mass into ammonium mass as Borek and the question itself have indicated.

Do they really use these units? I suppose it is in order to give the general public an idea they can appreciate of the concentrations?

For anyone knowing a bit of chemistry It sounds rather odd - ppm would be okay to give as a formula for somebody to weigh out grams to be put in a lake or something. You can weigh out sodium nitrate or calcium nitrate, but there is no substance called just 'nitrate' that you can weigh out.
 
epenguin said:
For anyone knowing a bit of chemistry It sounds rather odd - ppm would be okay to give as a formula for somebody to weigh out grams to be put in a lake or something. You can weigh out sodium nitrate or calcium nitrate, but there is no substance called just 'nitrate' that you can weigh out.

Come on, in many places we report things using proxies - like amount of P2O5 in fertilizer. For me NO3- doesn't sound worse than ammonia or just nitrogen, the meaning is obvious
 

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