In any engineering design problem, the first step is to understand the problem and identify one or more possible solutions. In this task, you’ll analyze the problems you face as the chemical engineer challenged with setting up the ammonia-making process. Recall the chemical equation for producing ammonia:
N2 + 3H2 ⇌ 2NH3 + energy
Part A
Explain the problem surrounding the ammonia-making process in terms of chemical equilibrium.
Part B
How can you change the chemical equilibrium to benefit the company? What benefits will be realized?
Part C
Design criteria are the desired features of a design. Identify at least two criteria for the design of the ammonia-making process. Explain why these criteria are important.
Part D
Le Chatelier’s principle describes how chemical equilibriums respond to changes in the concentrations of reactants or products. Think about how you can use Le Chatelier’s principle to find possible solutions to the design problem. Describe at least two ways to increase the yield (amount) of ammonia based on this principle.
Task 2
Simulating Possible Solutions
In this task, you’ll use a simulation to test a model for synthesizing ammonia. Recall the chemical equation for the reaction:
N2 + 3H2 ⇌ 2NH3 + energy
To begin, open the simulation and click the Rate experiments tab. Locate the Initial condition window in the top-right corner of the screen. In the Select a reaction drop-down menu, choose Design your own.
Part A
Look at the window on the left side of the simulation. It shows the reaction A + BC ⇌ AB + C. How does this reaction differ from the reaction by which ammonia is synthesized?
Part B
Decide which molecules in the simulation will represent the substances from the actual reaction. Include a strategy to deal with the difference in structure between the actual reaction N2 + 3H2 ⇌ 2NH3 and the simulated reaction. Not all molecules need to be used.
Part C
In the Options window of the simulation, select Pie to show the pie chart. In the window labeled Start with how many, use the up arrows to add 40 particles of A and 40 particles of BC. Then press the Begin experiment button. Wait a few seconds for the reaction to come to equilibrium, and then click pause near the bottom of the screen.
Study the graph on the left. The green line shows total average energy. The blue line shows the amount of potential energy possessed by the reactants and the products. Recall that substances most readily take the form in which they have the least potential energy. The amount of potential energy can be adjusted, affecting the outcome of the reaction. Recall that in the initial experiment for synthesizing ammonia, only about 20% of the reactants were converted to the products.
Click the Play arrow to resume the simulation. Then adjust the potential energy curve so the proportion of reactants to products is roughly the same as the proportion in the initial experiment. Adjust the center slider up or down so there’s a bump in the middle of the energy curve. The bump represents the energy the particles must have to react. Take a screenshot of the energy curve, and use the Insert Image button to paste it in the answer space.
Part D
In part D of task 1, you identified at least two ways in which the reaction of nitrogen and hydrogen could be changed to alter the equilibrium. Use the simulation to test those changes. Describe how you used the simulation to model the changes and the results they produced. Use these methods if you find them helpful:
Look at the pie graph to see how the system changes.
Use the Temperature slider at the bottom to cool or heat the mixture.
Click the pause button on the simulation to observe the number of particles at any point of time.
Part E
From your observations of the simulation, which strategy was most effective for quickly and efficiently producing ammonia? Why do you think this strategy is most effective?
Part F
Identify at least two limitations of the simulation. How do these limitations influence the simulation’s ability to model the synthesis of ammonia?
Task 3
Researching Solutions
In this task, you will conduct research and present your findings on the Haber process (also called the Haber-Bosch process) and its historical significance. In the Haber process, nitrogen and hydrogen are converted to ammonia. You will compare the Haber process with the results you obtained from the simulation. Your presentation will consist of 10 to 15 slides, built using presentation software.
Part A
When designing a science presentation, look for credible sources. Science doesn’t show bias, but humans do. Avoid sites and articles that provide facts without citing proper scientific evidence. You must be able to identify reliable sites so the data in your presentation is credible.
Use sources with URLs that end in .gov, such as CDC.gov. Government sites are reliable sources. You can also use sites with URLs ending in .edu. They are usually trustworthy, but sometimes students, rather than scientists, write content for .edu websites. Always identify the author of the source before proceeding. Some .org and .com sites are credible, but it’s important to verify their authenticity. When reviewing a source, ask these questions:
Who is the author?
Is this person a chemistry expert?
What is the document’s purpose?
Does the document state facts that scientists can support with evidence?
Are there opinions in the document?
How old is the document?
Do other credible sources support the statements in the document?
Search for credible websites or publications on the Haber process and its inventors. Write down at least two sources you will use for your presentation, and cite them using Modern Language Association (MLA) citation methods.
Part B
In a separate location, take notes from the sources you’ve identified. While taking notes from texts and websites, use these reading strategies. In the space provided, describe the key features of the Haber process you intend to use in your presentation.
Part C
Compare your proposed process for the synthesis of ammonia from part E of task 2 with the Haber process. Describe at least two similarities and two differences between the processes.
Part D
Create a presentation made up of 10–15 slides that explains the Haber process, including its inventors and historical significance. In the presentation, compare the principles used in the Haber process with the results of your investigation using the simulated reaction for the synthesis of ammonia. The presentation should follow a sequence like that of a five-paragraph paper, including an introduction and conclusion. Use your resources and notes from parts A through C to help you, and include images where appropriate.