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The Ostwald process for the commercial production of nitric acid from ammonia and oxygen involves the following steps:

4NH3(g)+5O2(g)------->4NO(g)+6H2O(g) -908 kj/mol (delta H)

2NO(g)+O2(g)----------->2NO2(g) -112 kj/mol

3NO2(g)+H2O(l)-------->2HNO3(aq)+NO(g) -140 kj/mol

Write the overall equation for the production of nitric acid by the Ostwald process by combining the preceding equations (Water is also a product).

So i know the answer is this...

"Multiply the equations so that the coefficients of the N-products become the same as the N-educts of the following line.
4NH3(g)+5O2(g)------->4NO(g)+6H2O(g) -908 kj/mol (delta H) (x3)
2NO(g)+O2(g)----------->2NO2(g) -112 kj/mol (x 6)
3NO2(g)+H2O(l)-------->2HNO3(aq)+NO(g) -140 kj/mol (x 4)

12NH3(g)+15O2(g)------->12NO(g)+18H2O(...
12NO(g)+6O2(g)----------->12NO2(g)
12NO2(g)+4H2O(l)-------->8HNO3(aq)+4NO.."

What i want to know is why do we multiply the equations like that? Am i missing a concept? Because why can we just not add the eqautions together?

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Keith Leannon
Keith LeannonLv2
28 Sep 2019

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Related questions

4NH3(g) + 5O2(g) ----> 4NO(g) + 6H2O(g)

2NO(g) + O2(g) ----> 2NO2(g)

3NO2(g) + H2O(l) ----> 2HNO3(l) + NO(g)

using the data in the Appendix plus the data below for nitricacid, calculate the values of deltaH0, deltaS0, deltaG0, and Keqfor each step. Then, assuming that the thermodynamic parametersdeltaH0 and deltaS0 are independent of temperature, calculate Keqat 825 degrees celsius

deltaH0 (kJ/mole) deltaS0 (J/K/mole) deltaG0 (kJ/mole)

-174 146 -81

I have been practicing some stoichiometryproblems in my text toprepare for a midterm this week. I solvedthe following problem,please let me know if you came up with thesame answer (please showwith your work):

OstwaldProcess:

1) 4NH3 (g) + 5O2 (g) --> 4NO (g)+6H2O (g)
2) 2NO (g) + O2 (g) --> 2NO2 (g)
3) 3NO2 (g) + H2O (l) -->2HNO3(aq) + NO (g)

What mass of NH3 must be used to yield1.0x106kilograms of HNO3 by the OstwaldProcess, assuming 100%yield in each reaction and the NO producedin the 3rd stage is notrecycled?

I came up with an answer of ~ 8.2x108grams ofNH3, I assumed that all products should equalthereactants in the next stage (if used in the next stage). I workedbackwards from HNO3. Please show your work and notsimple 'yes' or 'no' answers,thank you.

Nitric acid may be produced by oxidizing ammonia to nitric oxide over a platinum-rhodium catalyst, then oxidizing the nitric oxide to nitrogen dioxide in a separate unit where it is absorbed in water to form an aqueous solution of nitric acid. The three key reactions in the synthesis are the oxidation of the ammonia to nitric oxide and of nitric oxide to nitrogen dioxide, followed by dissolution of the NO2 in water:

4NH3(g)+ 5O2(g)→ 4NO(g)+ 6H2O(g)

2NO(g) + O2(g) → 2NO2(g)

4NO2 (g)+ 2H2O(l) + O2(g) → 4HNO3(aq)

In this problem, you may neglect side reactions that would lower the product yield. This would include the side reaction in which ammonia is oxidized to form nitrogen and water which can lower product yield.

4NH3 + 3O2 → 2N2 + 6H2O

Thus, for this project the overall reaction may be represented from the three key reactions above as:

NH3 + 2O2 → H2O + HNO3

Ammonia vapor at 275oC and 8 atm is mixed with air, also at 275oC and 8 atm, and the combined stream is fed to a converter. Fresh air entering the system at 30oC and 1 atm with a relative humidity of 50% is compressed to 100oC and 8 atm, and the compressed air then exchanges heat with the product gas leaving the converter. The quantity of oxygen in the feed to the converter is 20% in excess of the amount theoretically required to convert all the ammonia to HNO3. The entire process after the compressor may be taken to operate at a constant pressure of 8 atm.

In the converter, the ammonia is completely oxidized, with a negligible amount of NO2 formed. The product gas leaves the converter at 850oC and exchanges heat with the air leaving the system as described earlier. The product gas is then fed to a waste-heat boiler that produces superheated steam at 200oC and 10 bar from liquid water at 35oC. The product gas leaving the waste-heat boiler is cooled further to 35oC and fed to an absorption column in which the NO is completely oxidized to NO2 which in turn combines with water (some of which is present in the product gas). Water is fed to the absorber at 25oC, at a rate sufficient to form a 55 wt% aqueous nitric acid solution. Any NO formed in the reaction of NO2 to produce HNO3 is oxidized and the NO2 produced is hydrated to form still more HNO3. The off-gas from the process may be taken to contain only N2 and O2 and at 25oC and 1 atm.

b). Taking a basis of 100 kmol of ammonia fed to the process

(i) kmol of water fed to the absorber

(ii). Temperature of the product gas after it has exchanged heat with the air, assuming no heat is transferred between the heat exchanger and the surroundings

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