Chemistry - 9202 OxfordAQA

Production Of Ammonia And Sulfuric Acid C

Overview

Just over three quarters of every breath you take is nitrogen, and not one atom of it is any use to you. Plants cannot touch it either. The two nitrogen atoms in an N2 molecule are locked together so tightly that the gas drifts through the living world almost untouched, which is why farmland runs short of nitrogen long before it runs short of air. For most of human history the only answer was manure, crop rotation and patience. Then, in the early twentieth century, chemists worked out how to force that unreactive gas into a compound plants can absorb, and the ceiling on how many people the planet could feed lifted.

This lesson takes you inside the two largest chemical factories in the world: the one that turns air and natural gas into ammonia, and the one that turns yellow rock sulfur into the acid that industry uses more of than any other single chemical. You will meet the raw materials, the exact conditions in each reactor, and the reason the engineers running them deliberately settle for a low yield in one pass and then take the leftovers back to the start. It is the topic where the theory you have met about reversible reactions stops being an argument on paper and starts costing or saving real money.

Objectives

  1. The raw materials for the Haber process are nitrogen and hydrogen. Nitrogen is obtained from the air and hydrogen may be obtained from natural gas or other sources.
  2. Ammonia is a raw material in the production of fertilizers. Students should be able to explain the global need for fertilizers to maximise food yields.
  3. The purified gases are passed over a catalyst of iron at a high temperature (about 450 °C) and a high pressure (about 200 atmospheres). Some of the hydrogen and nitrogen react to form ammonia. The reaction is reversible so ammonia breaks down again into nitrogen and hydrogen: nitrogen + hydrogen ƒ ammonia On cooling, the ammonia liquefies and is removed. The remaining hydrogen and nitrogen are recycled.
  4. Sulfuric acid is produced industrially using the contact process. It is a three-stage process, which incorporates a reversible process and the use of a catalyst. Stage 1: Sulfur is burned in air to produce sulfur dioxide S (s) + O2(g) → SO2(g) Stage 2: Sulfur dioxide reacts with more oxygen to make sulfur trioxide 2 SO2(g) + O2(g) ƒ 2 SO3(g) This exothermic reaction is reversible and it requires a catalyst of Vanadium(V) oxide, V2O5, a temperature of around 450 °C and atmospheric pressure. Stage 3: Sulfur trioxide reacts with water to make sulfuric acid H2O(l) + SO3(g) → H2SO4(aq) Students should be able to describe the stages in the contact process and also to explain why a catalyst, a high temperature and atmospheric pressure are used in Stage 2.

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Lesson Note

A field of wheat strips nitrogen out of the soil every season and carries it away in the harvest. Put nothing back and the next crop is smaller, and the one after that smaller still. The nitrogen is not far away, because the atmosphere sitting on top of the field is mostly nitrogen gas, but crops have no way of prising an N2 molecule apart. What roots can absorb are dissolved ions such as the ammonium ion, NH4+, and the nitrate ion, NO3−, and until a little over a century ago the supply of those was set by bacteria, lightning and whatever manure a farmer could gather.

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Lesson Evaluation

Congratulations on completing the lesson on Production Of Ammonia And Sulfuric Acid C. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

  1. In the Haber process, the nitrogen and the hydrogen are obtained from: A. nitrogen from natural gas and hydrogen from the air B. nitrogen from the air and hydrogen from natural gas C. both gases from the air D. both gases from natural gas Answer: B
  2. Which conditions are used in the Haber process? A. about 450 degrees Celsius, about 200 atmospheres, an iron catalyst B. about 450 degrees Celsius, atmospheric pressure, a nickel catalyst C. about 25 degrees Celsius, about 200 atmospheres, an iron catalyst D. about 450 degrees Celsius, about 200 atmospheres, a vanadium(V) oxide catalyst Answer: A
  3. How is ammonia removed from the mixture of gases leaving the Haber reactor? A. It is burned off in air. B. It dissolves in water while nitrogen and hydrogen do not. C. It is cooled until it liquefies while nitrogen and hydrogen remain gases. D. It is filtered out through a fine mesh. Answer: C
  4. Which statement about the catalyst used in stage 2 of the contact process is correct? A. It is iron and it increases the yield of sulfur trioxide. B. It is vanadium(V) oxide and it increases the yield of sulfur trioxide. C. It is vanadium(V) oxide and it increases the rate but not the yield. D. It is iron and it increases the rate but not the yield. Answer: C
  5. Which equation represents the reversible stage of the contact process? A. S(s) + O2(g) to SO2(g) B. 2SO2(g) + O2(g) reversibly to 2SO3(g) C. H2O(l) + SO3(g) to H2SO4(aq) D. N2(g) + 3H2(g) reversibly to 2NH3(g) Answer: B

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