What is Ostwald's Process?

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Grade Level:

Class 12

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Definition

What is it?

Ostwald's process is a chemical method used to make nitric acid (HNO3) on a large scale. It involves three main steps: oxidation of ammonia, oxidation of nitric oxide, and absorption of nitrogen dioxide in water. This process is crucial for producing one of the most important industrial chemicals.

Simple Example

Quick Example

Imagine you want to make a special kind of fertilizer for your garden. Nitric acid, made by Ostwald's process, is a key ingredient in many fertilizers. So, this process is like the factory line that produces a very important component for growing healthy plants, much like how a dairy processes milk into paneer.

Worked Example

Step-by-Step

Let's see how much nitric acid can be produced if we start with 170 kg of ammonia (NH3) and the process is 80% efficient.

Step 1: Write the balanced chemical equations for the main steps.
4NH3 + 5O2 -> 4NO + 6H2O
2NO + O2 -> 2NO2
3NO2 + H2O -> 2HNO3 + NO

---Step 2: Calculate the molar mass of ammonia (NH3) and nitric acid (HNO3).
Molar mass of NH3 = 14 + (3 * 1) = 17 g/mol
Molar mass of HNO3 = 1 + 14 + (3 * 16) = 63 g/mol

---Step 3: Find the moles of ammonia available.
Moles of NH3 = Mass / Molar mass = 170,000 g / 17 g/mol = 10,000 moles

---Step 4: Use stoichiometry to find the theoretical moles of HNO3 produced from NH3.
From the balanced equations, 4 moles of NH3 eventually produce 4 moles of NO, then 4 moles of NO2, and finally, 4 moles of NO2 can produce (4/3) * 2 = 8/3 moles of HNO3.
So, 4 moles NH3 -> (8/3) moles HNO3. This simplifies to 1 mole NH3 -> (2/3) mole HNO3.
Theoretical moles of HNO3 = 10,000 moles NH3 * (2/3) = 6666.67 moles HNO3

---Step 5: Calculate the theoretical mass of HNO3.
Theoretical mass of HNO3 = Moles * Molar mass = 6666.67 moles * 63 g/mol = 420,000 g = 420 kg

---Step 6: Apply the 80% efficiency.
Actual mass of HNO3 = Theoretical mass * Efficiency = 420 kg * 0.80 = 336 kg

Answer: 336 kg of nitric acid can be produced.

Why It Matters

Ostwald's process is vital for making nitric acid, which is used in fertilizers to boost crop yields for our farmers. It's also key in producing explosives for mining and construction, and dyes for textiles. Engineers, chemical scientists, and even agricultural experts rely on this process to create essential products that impact our daily lives, from the food we eat to the clothes we wear.

Common Mistakes

MISTAKE: Students often forget that the process involves multiple steps and don't balance all intermediate reactions. | CORRECTION: Always write down and balance all three main chemical equations involved in the Ostwald's process to ensure correct stoichiometric calculations.

MISTAKE: Confusing the catalysts used or the conditions for each step. | CORRECTION: Remember that platinum-rhodium gauze is used as a catalyst in the first step (ammonia oxidation), and specific temperatures and pressures are maintained for optimal yield.

MISTAKE: Not accounting for the recycling of NO in the final absorption step. | CORRECTION: The NO produced in the third step (3NO2 + H2O -> 2HNO3 + NO) is recycled back to the second step (2NO + O2 -> 2NO2) to improve overall efficiency and reduce waste.

Practice Questions

Try It Yourself

QUESTION: What is the main raw material used in Ostwald's process? | ANSWER: Ammonia (NH3)

QUESTION: Name the catalyst used in the first step of Ostwald's process and state its purpose. | ANSWER: Platinum-rhodium gauze. It helps speed up the reaction of ammonia with oxygen to form nitric oxide.

QUESTION: If 340 kg of ammonia (NH3) is completely converted into nitric acid (HNO3) with 75% efficiency, calculate the mass of HNO3 produced. (Molar mass NH3 = 17 g/mol, HNO3 = 63 g/mol) | ANSWER: Step 1: Moles of NH3 = 340,000 g / 17 g/mol = 20,000 moles. Step 2: From stoichiometry (1 mole NH3 -> 2/3 mole HNO3), Theoretical moles of HNO3 = 20,000 * (2/3) = 13333.33 moles. Step 3: Theoretical mass of HNO3 = 13333.33 moles * 63 g/mol = 840,000 g = 840 kg. Step 4: Actual mass of HNO3 = 840 kg * 0.75 = 630 kg.

MCQ

Quick Quiz

Which of the following is NOT a step in Ostwald's process?

Oxidation of ammonia to nitric oxide

Oxidation of nitric oxide to nitrogen dioxide

Absorption of nitrogen dioxide in water

Reduction of nitrogen dioxide to nitrogen

The Correct Answer Is:

Options A, B, and C are the three main steps of Ostwald's process for producing nitric acid. Option D, reduction of nitrogen dioxide to nitrogen, is not part of this process.

Real World Connection

In the Real World

In India, companies like IFFCO (Indian Farmers Fertiliser Cooperative Limited) use processes similar to Ostwald's to produce large quantities of nitric acid. This acid is then used to make urea and other complex fertilizers, helping Indian farmers grow more food and ensuring food security for our country. It's a fundamental process supporting our agricultural backbone.

Key Vocabulary

Key Terms

OXIDATION: A chemical reaction involving the loss of electrons or gain of oxygen. | CATALYST: A substance that speeds up a chemical reaction without being consumed itself. | STOICHIOMETRY: The calculation of quantities of reactants and products in chemical reactions. | NITRIC ACID (HNO3): A strong, corrosive mineral acid used in fertilizers and explosives. | AMMONIA (NH3): A compound of nitrogen and hydrogen, a key raw material.

What's Next

What to Learn Next

Now that you understand Ostwald's process, you can explore the 'Contact Process' for manufacturing sulfuric acid. Both are important industrial processes, and learning about the Contact Process will show you how different acids are made and their diverse applications, helping you connect more dots in industrial chemistry!