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Most students learn one sentence about catalysts: they speed up a reaction without being used up. That sentence is largely Wilhelm Ostwald's work. He also used it to solve a real industrial problem, turning ammonia into nitric acid. This post covers how he thought about catalysts, what his patent actually says, a worked calculation, and where the topic sits in your syllabus now.
Who was Wilhelm Ostwald?
The Nobel Prize facts page records that Ostwald was born on 2 September 1853 in Riga, now in Latvia, and died on 4 April 1932 near Leipzig. He won the 1909 Nobel Prize in Chemistry "in recognition of his work on catalysis and for his investigations into the fundamental principles governing chemical equilibria and rates of reaction."
His Nobel biography adds that he became Professor of Physical Chemistry at Leipzig in 1887, founded and edited the Zeitschrift für physikalische Chemie from that year, and wrote widely used textbooks. His work on electrolytes led to the dilution law named after him, which you meet in ionic equilibrium; see our post on degree of dissociation and Ostwald's dilution law.
What did Ostwald say a catalyst does?
Before Ostwald, the Swedish chemist Berzelius had given catalysis its name, but, as Ostwald notes, deliberately offered no explanation of it. Ostwald studied the rates of many reactions, including reactions run in the presence of acids. In his Nobel lecture, On Catalysis, he describes his key step as "conceiving catalytic phenomena as accelerations of possible processes which are in progress." He writes that he was "compelled to the view that the nature of catalysis is not be sought in the inducement of a reaction, but in its acceleration," and dates the publication setting this out to 1888.
That is the view in your textbook. The NCERT Class 11 chapter Equilibrium says a catalyst "increases the rate of forward and reverse reactions that pass through the same transition state and does not affect equilibrium." The NCERT Class 12 chapter on chemical kinetics adds that it lowers the activation energy and "does not change the equilibrium constant of a reaction rather, it helps in attaining the equilibrium faster."
What problem did the Ostwald process solve?
People knew that ammonia and oxygen react over a catalyst to give nitrogen oxides, but only as a laboratory curiosity. Ostwald's US patent 858,904, Process of manufacturing nitric acid, filed on 26 June 1902 and granted in 1907, explains why it had failed on a large scale. Two reactions compete on the catalyst: ammonia is oxidised to nitrogen oxides, and those valuable oxides are then broken down into worthless free nitrogen. So, unlike most catalytic processes, longer contact with the catalyst makes the yield worse.
His solution was to push the gas through a thin layer of catalyst very fast: "it has been found advantageous to allow the gases to be in contact with the catalytic agent for about one-hundredth of a second," using platinum, with the gas kept above 300 °C. The hot product gases were also used to preheat the incoming mixture.
A worked example: nitric acid from one tonne of ammonia
In modern notation the steps are usually written as:
4NH₃ + 5O₂ → 4NO + 6H₂O (over the platinum catalyst)
2NO + O₂ → 2NO₂
3NO₂ + H₂O → 2HNO₃ + NO (the NO is recycled)
Add them up with the recycling and the net change is NH₃ + 2O₂ → HNO₃ + H₂O. Check it: one N on each side; three H on the left, one plus two on the right; four O on the left, three plus one on the right.
So one mole of ammonia can give at most one mole of nitric acid.
Moles of NH₃ in 1,000 kg: 1,000,000 g ÷ 17.03 g/mol = 58,720 mol.
Mass of HNO₃: 58,720 mol × 63.01 g/mol = 3.70 × 10⁶ g, or 3,700 kg.
One tonne of ammonia can give at most about 3.7 tonnes of nitric acid. The common mistake is to use the last step alone and conclude that only two-thirds of the nitrogen ends up as acid. That ignores the recycled NO. For the maximum overall yield, use the net equation.
The ammonia itself came from the Haber process, where NCERT notes an iron catalyst lets the reaction run at a useful rate; see our post on Fritz Haber and ammonia.
Is the Ostwald process still in the syllabus?
Check carefully. The current rationalised NCERT Class 11 and 12 chemistry books no longer have a chapter on the p-block elements of groups 15 to 18, where nitric acid used to be covered. The JEE (Main) 2026 syllabus lists the p-block only as general trends, while catalysts appear in both the equilibrium and the kinetics units. Read the current year's syllabus for your own exam. The catalyst ideas are safe to learn either way.
If your errors in kinetics come from setting up the wrong rate law, the Fermi Problem Library has a step-by-step solver that explains the reasoning behind each step.
What can a student take from Ostwald?
Define the idea precisely. "Accelerates a reaction that can already happen" is sharper than "makes reactions happen."
Look for the competing process. His patent works because he saw that the catalyst also destroyed the product.
Measure, then control. The contact time was found by experiment, by speeding the gas until unreacted ammonia began to appear.
Tonight, write the three Ostwald process equations, add them to get the net equation, and check every atom.
