Advanced Topic 478 of 1102 Kinetics & Equilibrium
Ostwald Process
Nitric acid is made by catalytic oxidation of ammonia on platinum-rhodium gauze.
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In-depth explanation of Ostwald Process
The Ostwald process is the industrial route to nitric acid, starting from the catalytic oxidation of ammonia. Ammonia is oxidized with air over a platinum-rhodium gauze catalyst at about 900 degrees C to give nitrogen monoxide, which is then oxidized further to nitrogen dioxide. The nitrogen dioxide is absorbed in water, forming nitric acid together with nitrogen monoxide that is recycled. The high temperature and short contact time are chosen to maximize the yield of NO and minimize the formation of nitrogen gas. Nitric acid made this way is the basis of much fertilizer and explosives production.
Going deeper: Ostwald Process
Key ideas: Three stages: 4NH3 + 5O2 -> 4NO + 6H2O over Pt-Rh gauze at about 900 degrees C and 4 to 10 atm, 2NO + O2 -> 2NO2 after cooling, and 3NO2 + H2O -> 2HNO3 + NO with the NO recycled. The first step is very exothermic and nearly self-sustaining once started, and yields of NO reach 95 to 98 percent. Product acid is about 60 percent HNO3 and is concentrated by distillation with a dehydrating agent.
Common mistakes and connections: Students mix the process up with Haber or contact process or forget that ammonia is itself the feedstock from the Haber process. Another mistake is thinking NO2 is absorbed in water with no by-product, whereas NO forms and is recycled. High contact time lowers the yield because N2 forms. Related to catalysis and to fertilizer and explosives chemistry.
Visualization of Ostwald Process
Nitrogen is oxidised stepwise from -3 in ammonia to +5 in nitric acid: NH3 to NO over Pt-Rh, NO to NO2, then NO2 absorbed in water. The interactive lesson shows this as a live animation or chart.
Worked example and use case
The first step is 4NH3 + 5O2 -> 4NO + 6H2O over a platinum-rhodium catalyst.
Frequently asked questions about Ostwald Process
What is Ostwald Process?
Nitric acid is made by catalytic oxidation of ammonia on platinum-rhodium gauze.
Is Ostwald Process a beginner, intermediate or advanced topic?
Ostwald Process is a advanced topic in Kinetics & Equilibrium. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Ostwald Process?
Study these earlier topics in Kinetics & Equilibrium first: Effect of Catalyst on Equilibrium, Haber Process, Contact Process.
What comes after Ostwald Process?
The next topics in Kinetics & Equilibrium are Equilibrium and Free Energy and Solubility Product.
Can I practise Ostwald Process with quizzes?
Yes. The interactive lesson includes a self-check question on Ostwald Process, and the Kinetics & Equilibrium quiz draws on every topic in this area.
Where Ostwald Process fits in Kinetics & Equilibrium
Ostwald Process is topic 59 of 91 in Kinetics & Equilibrium.