Video: Making ammonia and the Haber Process

﻿Hello, and welcome to our next lesson in the using resources topic. Today's lesson is all about making ammonia in 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 the use of nitrogen-based fertilisers. From there, we will look at why ammonia is important, and then we will start looking at something called the Haber process. And we will look at where the raw materials come from, before looking at an overview of the whole process. And you will finish the lesson off by doing the quiz. So nitrogen-based fertilisers, are fertilisers which contain nitrogen. Now fertilisers are used by farmers to help their crops to grow. Nitrogen is needed for the plants to be able to make their proteins. Proteins are needed for growth. Now, plants are only able to take up soluble nitrate ions, as opposed to being able to absorb the nitrogen that we find in the air. Now, plants take up these soluble nitrate ions through their root hair cells, from the soil. Now what happens, the reason why nitrogen-based fertilisers are needed in the first place, is when the crops are harvested, the nitrogen is removed. So we're going to look at why in particular, ammonia is important in making nitrogen-based fertilisers. So there's 78% nitrogen in the atmosphere. However, nitrogen gas is insoluble in water, so plants can't just take up nitrogen from the air. And so plants need the soluble form. And the soluble form, comes in the form of soluble nitrate ions. And it's through a process called, fixing nitrogen. Now this is when nitrogen from the air is converted into a soluble form, which plants are able to take up. This is in the form of nitrate ions. So we're going to do a series of quickfire questions just to check what we've done so far. So nitrogen is used in plant fertilisers. Well done if you selected true. Plants need nitrogen in order to make carbohydrates. Well done if you selected false. Remember plants need nitrogen to make proteins. Plants absorb nitrate ions through their leaves. Well done if you selected false. Remember plants absorb nitrate ions through their root hair cells in the soil. Nitrogen is removed from the land when crops are harvested. Well done if you selected true. This is why nitrogen-based fertilisers are needed. 85% of the atmosphere is made up of nitrogen. Well done if you selected false. Remember 78% of the atmosphere is made up of nitrogen. Nitrogen gas is soluble in water. Well done if you selected false. Nitrogen gas is insoluble in water. So what I would like you to do now, is you have got a series of five questions, I would like you to pause the video, and answer the questions, and then press Play once you have finished. So please pause the video now. Okay, fantastic. Let's go through the answers then. Hey, please pause the video now to mark your work. Anything you didn't get correct, please make sure you write the correct answer in, and then press Play again. Okay, so we are going to move on, and we're going to look at something called the Haber process. Now the Haber process, is a way of turning nitrogen in the air, into ammonia. And it was first devised in a reaction about 100 years ago. And it was first devised by a German chemist called, Fritz Haber, whose picture you can now see on the slide. And it's a method that is still used now to make ammonia. So what is needed to make ammonia? So we can see here, a dots and cross diagram of ammonia. It is made up of both nitrogen and hydrogen. So it's made up of one nitrogen atom, and three hydrogen atoms. Nitrogen and hydrogen are both nonmetals, and so the bonding found in ammonia is covalent bonding. So, we use nitrogen from the air, and we use hydrogen. And the hydrogen mainly comes from natural gas. If you are a higher Tisch student, next lesson, we will look at how these raw materials are extracted, in more detail. So this diagram here, shows the main stages of the Haber process. And I'm going to talk you through it step by step. So the first stage is that the nitrogen from the air, and the hydrogen from the natural gas, are pumped through the pipes. The second stage is they move into a compressor. And what happens in the compressor, is that the pressure is increased to 200 atmospheres. If you are a higher Tisch student, next lesson, we will be looking at the compromise in the conditions, when it comes to pressure, and temperature. Next thing that happens, so the gases have been compressed, and they are now at 200 atmospheres pressure. They then move in to the next section of the process. So the pressurised gases of nitrogen, and hydrogen, are heated to 450 degrees celsius, and they're passed through a tank with an iron catalyst. Now remember how catalysts work, is they speed up the rate of reaction by lowering the activation energy. Remember activation energy, is the minimum amount of energy needed for the reaction to start. The next stage. So what happens, because you have increased the temperature, you're at 200 atmospheres pressure, you have the iron catalyst, what happens, is that the nitrogen, and the hydrogen, react together, and they form ammonia. So what you can see in the diagram just above step number four, is when they leave the step number three tank, you have ammonia coming out as a gas, and you have unreacted nitrogen, and unreacted hydrogen, also coming out as gases. So what happens in step number four, is that the mixture is cooled, and this causes ammonia to liquefy. So it changes from a gas, into a liquid. Remember when it changes from a gas to a liquid, we call that state change, condensation. The liquid ammonia is then able to be removed. and then step number five, so the unreacted nitrogen, and hydrogen, are able to be recycled. So they don't just go to waste. But what has to happen before they can be reused, is that they get recompressed, and heated before they return to the reaction vessel. And you can see in the diagram, where they rejoin, is before it goes into the tank where the catalyst is. Hey, this is the chemical reaction which is taking place. So nitrogen plus hydrogen makes ammonia. Now, hopefully from earlier on in the chemistry course, you recognise the symbol between the hydrogen, and ammonia. Can you remember what that symbol means? Well done if you've remembered that is the symbol for a reversible reaction. So remember a reversible reaction, is when the reaction can go either way. So nitrogen, and hydrogen, can react together to make ammonia, but ammonia can also be broken down to make hydrogen, and nitrogen. And what we've got here, is the balanced symbol equation. So nitrogen is diatomic, so that means that two nitrogen atoms go together. So we've got N2. And nitrogen is found in the gaseous state. So we use the state symbol G. Nitrogen reacts with hydrogen. So hydrogen is H2. Now, we have three moles of hydrogen, and so that's shown by the big three in front of the H2. And again, hydrogen is gaseous, so we use the state symbol G. So one mole of nitrogen reacts with three moles of hydrogen. They react together to form ammonia. Now the formula for ammonia is NH3. But in order for it to be a balanced symbol equation, we need to put a two in front of the NH3, to make sure we have an equal amount of atoms on each side. Ammonia is also in the gaseous state, so we use the state symbol G. So one mole of nitrogen reacts with three moles of hydrogen to make two moles of ammonia. So we're going to do a series of quickfire questions to check your understanding for this lesson. So the raw materials in the Haber process, are nitrogen, and hydrogen. Well done if you selected true. The chemical formula for ammonia is NH2. Well done if you selected false. The chemical formula for ammonia, is NH3. The reaction in the Haber process is a reversible reaction. Well done if you selected true. The conditions used in the Haber process is 200 atmospheres, and 450 degree celsius. Well done if you selected true. As I've mentioned before, if you are a higher Tisch student, next lesson, we will look at the compromises that are made in the Haber process, looking at pressure, and temperature. Unreacted nitrogen, and hydrogen, are disposed of in the Harbour process. Well done if you selected false. That unreacted nitrogen, and hydrogen, are recycled in the Haber process. So, what's going to happen now, is we've got five questions on the slide, I would like you to pause the video now, and write the answers down. Once you have finished, please press Play, so we can go through the answers. So please pause the video now. Okay, so let's go through the answers. So please pause the video now, to mark your work. Please make sure that you write in any answers you didn't get correct, and press Play once you have finished. Okay, so let's do a recap of what we have learned this lesson. So most fertilisers contain nitrogen. Remember nitrogen is needed by plants to make proteins. Proteins are needed for plants to be able to grow. The Haber process uses nitrogen, and hydrogen, to form ammonia. Remember the nitrogen comes from the air, and the hydrogen normally comes from natural gas, which is a fossil fuel. The conditions used are 200 atmospheres pressure, 450 degrees celsius, and an iron catalyst. Any unreacted hydrogen, and nitrogen, are recycled. Well done on another super lesson. Please make sure that you now click Next, to complete the quiz for this lesson.

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Completed: Making ammonia and the Haber Process

This lesson will look at why ammonia is such an important compound. We will look at the Haber process and the different conditions that are used.

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Making ammonia and the Haber Process

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