Video: The economics of the Haber Process

﻿Hello, and welcome to this higher-tier-only lesson on the economics of the Haber process. Please make sure that you have a pen, and a piece of paper ready, and that your phone is on silent, and at one side so that you don't get distracted. So once you're ready, let's go. So what we're going to start off by looking at, is recapping what we did last lesson, where we looked at the Haber process. We will then move on, and we will look at the effect of temperature, concentration, and pressure on the yield of ammonia. We will then look at why their industrial conditions are a compromise, before we interpret some graphs linked to the industrial production of ammonia, and then you will complete the quiz to finish off. So we're going to do a series of quickfire questions just to check what you remember from last lesson. So the raw materials in the Haber process are nitrogen, and hydrogen. Well done, if you selected true. Unreacted nitrogen, and hydrogen, are disposed of in the Haber process. Well done, if you selected false. Remember that unreacted nitrogen, and hydrogen, are recycled in the Haber process. The reaction in the Haber process is a reversible reaction. Well done, if you selected true. The conditions used in the Haber process are 200 atmospheres, and 450 degrees celsius. Well done, if you selected true. So what we're going to do, is we're going to look at, the economics of the Haber process. So it's sort of the money side of the Haber process, and the conditions needed. So we're going to start off by looking at how the raw materials are extracted. Remember the raw materials are nitrogen, and hydrogen. Now, nitrogen, the air is made up of 78% nitrogen. And so what happens to extract the nitrogen to be able to use in the Haber process, is a process called fractional distillation, which you should have looked at earlier on in the chemistry course happens for liquid air. And in order for air to liquefy, the temperature has to drop to -200 degree Celsius and also high pressure pumps have to be used. So it's relatively expensive to extract the nitrogen from the air to then use in the Haber process. The other raw material is hydrogen. Now we get hydrogen from natural gas and what happens is methane reacts with steam and you form hydrogen, which we use in the Haber process and carbon monoxide and very high temperatures are used in the extraction of hydrogen. So again, it's a relatively expensive process and methane we buy as natural gas. So before we move on and we look at the economics behind the Haber process, there's just a couple of key concepts that we need to go through that you will have looked at earlier on in the GCSE chemistry course. So the first is making sure you understand what equilibrium is. So equilibrium is when the rate of the forward reaction is the same as the rate of the backwards reaction in a closed system. So you will have looked at this earlier on in the chemistry course, you also will have been introduced to something called Le Chatelier's principle. Now, what Le Chatelier's principle states, is that if a change is introduced to a system in equilibrium, the position of equilibrium will shift to oppose the change. Now, this is going to be key in our understanding of the effect of pressure and temperature on the production of ammonia in the Haber process. So we've looked at equilibrium, Le Chatelier's principle, and now we're just going to make sure you know, what is meant by yield. So when we talk about yield, we're looking at the amount of product, which is actually made compared to the amount that would be made. If all of the raw materials, all of the reactants were used up. So we're going to start off by looking at the effect of pressure. So you saw this equation last lesson. So one mole of nitrogen will react with three moles of hydrogen and you will end up forming two moles of ammonia. Now, remember it's a reversible reaction. That's what arrow showing it's a reversible reaction. So that means that two moles of ammonia can break down to make one mole of nitrogen and three moles of hydrogen. So, on the left hand side, on our reactant side, we have four moles of gas because we have one mole of nitrogen and we have three moles of hydrogen. On our product side, on the right hand side, we have two moles of gas because there's two in front of that NH3. Now it's really important, when we're talking about the effect of pressure and Le Chatelier's principle., this only applies to gaseous substances. So it's worth noting that nitrogen, hydrogen and ammonia are all in the gaseous state. So we include all of that when we're looking at pressure. So, if we have an increase in pressure, remember Le Chatelier's principle states that the position of equilibrium will shift to oppose the change. So if there is an increase in pressure, what will happen is the position of equilibrium will shift to try to decrease the pressure. So that means the position of equilibrium will shift to the side, which has fewer moles of gas, because the less moles of gas there is the less pressure that's going to be exerted. So in this case, what will happen is the position of equilibrium will shift to the rights. It will favour the product side. And as I have mentioned, it shifts to the right to reduce the pressure because it's opposing the change. So it shifts to the side, which has less moles. So if we wanted to have a really high yield of ammonia, we would want our reaction to be under very high pressure because with a high pressure, it, the position of equilibrium shifts to the right, and we end up producing lots of ammonia. However, there are some problems with using really high pressure, lots energy is needed to compress the gases. And because you're using very high pressure, you would need really expensive reaction vessels and pipes in order to avoid explosions. So what happens in the Haber process is actually that there is a compromise with the pressure used. So you might remember from last lesson, the compromise is they use 200 atmospheres pressure. And so what this means is that we end up with a lower yield of ammonia, but the plus side of using a lower pressure is that there's reduced costs. So remember, economics is all to do with money. Later on in the lesson, we will have a look at some graphs and you will be able to see the difference in using low pressures and higher pressures when it comes to the yield of ammonia. So just going to do a series of quick fire questions to check what we have learnt so far. So fractional distillation is used to extract nitrogen from liquid air. Well done. If you selected true. The cooling down of air doesn't require any energy. Okay, the answer to that is false. The cooling down of air does require quite a lot of energy. And hence the costs associated. Hydrogen is made by reacting methane steam. Well done, If you selected true. A low pressure will give a high yield of ammonia. Well done, If you selected false, remember a high pressure will give a high yield of ammonia because the position of equilibrium will shift to oppose the change. So it will favour the side with less gaseous moles. If the pressure is increased, the reaction favours the side with fewer moles. Well done, if you selected true. So what I would like you to do, there are 6 questions on the slide now. I would like you to pause the video and I would like you to answer the questions. Once you all finished, please press play and we can mark your work. So please pause the video now. Okay, So let's mark your work. Please pause the video now, to mark your work, make sure you writing anything you didn't get correct. And then press play once you are done. Okay. So let's move on and let's look at the effect of temperature on the reaction in the Haber process. So the forward reaction is an exothermic reaction. Remember what that means is that energy is given out to the surroundings and it causes the surroundings to increase in temperature. So if the forward reaction is exothermic, that must mean that the backwards reaction is endothermic. Remember endothermic is when energy is taken in from the surroundings and it causes the surroundings to decrease in temperature. So, we're interested in making ammonia and we know that the forward reaction is exothermic. So if there was a reduction in temperature, what's going to happen is the position of equilibrium will share shift to oppose this change. So what we'll try to do is try to increase the temperature. So to increase the temperature, it's going to favour the exothermic reaction. So the position of equilibrium will shift to the right. So we will end up with a higher yield of ammonia. So if we use a low temperature, because remember that's when we're going to end up with a higher yield of ammonia, the problem with it is that the rate of reaction is really slow because the particles have less kinetic energy and there is going to be less successful collisions between the particles. And because the rate of reaction is really slow, If we use a low temperature and the plant is really expensive to run, we need to be making as much ammonia as possible in a shorter time period as possible. So what happens is that there is actually a compromise with temperature. If you remember from last lesson, the temperature, which is used in the Haber process is 450 degrees Celsius. Now we end up with a reasonable rates of reaction. The particles have more kinetic energy. Therefore, there are more successful collisions between the particles and an increased rates of reaction. However, it does mean that there is a lower yield of ammonia being produced, but there has to be a compromise. So if you remember from last lesson, the Haber process runs at 200 atmospheres, 450 degrees Celsius, and there is a catalyst present. Now the catalyst present is Iron and how the catalyst works, how the iron catalyst works is it speeds up both the forwards and the backwards reaction at the same rate. So it doesn't actually affect the yield of ammonia being produced because it speeds up both the forwards and backwards reaction at the same rates. However, ammonia is produced more quickly. So we don't end up, remember the yield is how much product you have compared to how much you would have if all the reactants were used up, what happens with the catalyst is we just make ammonia more quickly. So we're going to do a series of quick fire questions to check what you have learned so far. So the forward reaction in the Haber process is an endothermic reaction. Well done, If you selected false. The forward reaction is an exothermic reaction. Decreasing temperature will increase the yield of ammonia. Well done, if you selected true. Remember the position of equilibrium will shift to oppose the change. So if you decrease the temperature, it will favour that exothermic reaction. In this case, the exothermic reaction is the forward reaction. So we would have an increased yield of ammonia. More collisions of gaseous particles occur at a lower temperature. Well done, If you selected false. Remember the higher the temperature, the more collisions that are. An iron catalyst is used in the Haber process. Well done, If you selected true. A catalyst increases the yield of ammonia. Well done. If you selected false. Remember the catalyst doesn't increase the yield, It just affects how quickly ammonia is made. So what I would like you to do, you've got 5 questions. I would like you to pause the video now, answer the questions. And once you have finished, please press play.so we can mark the answers. So please pause the video now. Excellent, Let's mark your work. Please pause the video now to mark your work, correct any answers you didn't get, right. And then press play once you are done. So final thing, we're going to look up before you do the end of lesson quiz. We're going to look at interpreting some graphs on the Haber process. So at the bottom of the graph on the X-axis, we've got the pressure in atmospheres and on the Y-axis, we've got the yield of ammonia being produced. Remember the higher the yield, the more the reactants have been used up. So a high yield of ammonia is a really good thing. So we have got pressure. We've got the percentage yield and then we've got five different temperatures. So we know that if we have a higher pressure, we are going to end up with a higher yield of ammonia. But remember the problems show associated with having a high pressure and in terms of actually producing the ammonia. And this is shown by if you have a look at 400 atmospheres pressure, the yield is at its highest compared to if you had a pressure of a 100 atmospheres. The other thing is temperature. So we know that if you reduce the temperature, the higher the yield that you will end up with. This is shown by looking at 350 degrees Celsius. The yield of ammonia is nearly about 65%. If you come at, sorry, I should say at 450 atmospheres pressure. If I was to compare that to a much higher temperature. So 550 degrees Celsius also at 450 atmospheres, the yield of ammonia is now down to about 22%. But remember the problem with having a lower temperature is that there are less frequent particle collisions. And so we have a much slower rate of reaction and not just not as economic in the process. So it's quite common for you to have, have a graph like this, and you have to interpret it. So, if I said, for example, what is the yield of ammonia at 450 degrees Celsius and 200 atmosphere's pressure. Now that is actually the conditions which are used in the Haber process. So what I'm going to do is I'm going to go along my X-axis to 200 atmosphere's pressure, and I'm going to go up to where 450 degrees Celsius is. And then I'm going to read across onto the Y-axis. And I can see that at 200 atmospheres and at 450 degrees Celsius, the yield of ammonia is about 35%. So what I would like you to do is you're going to have a go at interpreting this graph. So you've been given different temperatures and different pressures, and I would like you to work out what the approximate yield is at those conditions. So, if you can please pause the video now and do those 5 questions, and then what you all finished, please press play. And we will go through the answers. It's worth noting that I given a percentage range as acceptable answers. So please pause the video now. Okay, so the answers are now on the slide, except for part D there is an acceptable range in which your answers can be. So if your answers fell within that range, you can give yourself the mark. So please pause the video now to mark your work. Hi, let's recap what we have learned during this lesson. The yield is the amount of product made compared to the amount we would make, If all the reactants were used up. Increasing the pressure increases the yield of ammonia. Decreasing the temperature increases the yield of ammonia. And the compromise conditions therefore, are 450 degrees Celsius and 200 atmospheres pressure. So well done on all your hard work throughout this lesson. Please make sure that you now click next to complete the end of lesson quiz.

Worksheet: The economics of the Haber Process

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Completed: The economics of the Haber Process

This lesson will look at the Haber Process and the need for compromised conditions in the manufacturing process. We will look at the effect of temperature and pressure on the yield of ammonia as well as the importance of a catalyst.

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The economics of the Haber Process

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