Good day, great tense. In this last lesson in the reactions and equestolution section, we're learning about iron exchange reactions. What is an iron exchange reaction? It's a reaction with positive ions exchange the respect of negative ions due to a driving force. And there are four types of iron exchange reactions, this precipitation, gas forming, acid base and redox reactions. Now we've seen most of these reactions before we just haven't labelled them as such. Let's start off with the precipitation reaction. So we can take sodium chloride and we're going to add... The subonitrate is added to a sodium chloride solution forming a precipitate of silver chloride. So you saw that sodium chloride when it's added to a subonitrate or vice versa, it forms a white precipitate. So the equation for that is nA plus CL minus plus silver nitrate. And watch here, there's the sodium plus. It is joining up with a negative nitrate, or sorry. Yes, you could have nitrate to form sodium nitrate. And yeah, your silver plus is joining up with your chloride minus to form your silver chloride solid or precipitate. This area means precipitate. So there you can see a clear indication of the ion exchange reaction that's occurring. Now let's talk about gas forming reactions. We've actually seen a similar reaction like this before. In fact, we've seen exactly the same one, just a different video now. We're going to take sodium carbonate and we're going to add hydrochloric acid. From what you learned in the last lesson, we're going to test it for carbonate. What do you expect to form? We're investigating the reaction between sodium carbonate and hydrochloric acid. Lime water is used to test whether the gas given off is carbon dioxide from the reaction. Lime water turns cloudy in the presence of carbon dioxide. Hydrochloric acid is the common name for hydrogen chloride. Yes, it is added to the conical flask, first of all. The flexible delivery tube is used to make sure that any gas given off in the reaction will bubble through the lime water. Sodium carbonate is then added to the flask. A rubber stopper is used to make sure that all of the gas given off goes down the flexible chip to the lime water. Notice that the solution is as indicating that a gas is given off. Also notice the bubbles of gas bubbling through the lime water in the test tube. The lime water is seen to go cloudy with the gas as bubble through it. This shows that carbon dioxide was the gas being given off in this reaction. What you should have said at the end, before I showed you the video, was that you expected carbon dioxide to be given off. We were testing using lime water and it would go milky. Let's look at the equation to check. We've got sodium chloride, sodium chloride N2CO3, plus HCl forms sodium carbonate, plus HCl forms sodium chloride plus water plus carbon dioxide. Sodium here, which is your positive, is joining up with a negative chloride ions to form sodium chloride. Interestingly, because you've got a carbonate and acid, it always splits up the rest of the form water and carbon dioxide. That's an example of a gas forming reaction. Now let's look at as-based reactions. Ascent bases when added together always give you a salt and water. Let's look at an example of that. I hope you realized that it was quite an atomic reaction. It was quite a fast reaction. Let's look at the equation. We've got sodium hydroxide plus HCl forms sodium chloride and water. In this case, the salt here, that we're talking about here, happens to be sodium chloride, which is table salt. But this salt here that I'm talking about is not always table salt. It is just meaning a substance which dissolved in water forms an ionic solution. Now let's look at this reaction. Sodium positive joins up with a negative chloride to form sodium chloride and the hydrogen from this molecule joins up with hydroxyl to form the water. Do you see how beautifully we've had ionic exchange reaction here? Now let's look at redox reactions. Redox reactions basically require the transfer of electrons. There is a change in the charge of atoms. Let's look at this little reaction. So magnesium is burning in oxygen. Magnesium as an element has a charge of zero. But when it joins up with oxygen, it suddenly has a charge of 2 plus. Oxygen as a diatomic molecule has a charge of zero. But suddenly it has a charge of 2 minus when it is with magnesium oxide. So we can see that magnesium and oxygen have transferred electrons to become magnesium oxide. Let's look at another example. So we have our conqueror. Add the nice acid. Now let's look at the reaction. Now water. Now water. That was a pretty cool video. I hope you enjoyed all the facial expressions of the kids behind the experiment and actually looked at the experiment. We took a cup and added nitric acid. And he ended up with copper nitric. That horrible gas that was this N02. And you ended up with water. Now what happened was the reason he added more water at the end was that he was actually shoving the reaction back. And basically he was adding the water. And the water in blue like that to show the free copper ions. Okay, so copper plus the nitric acid. See that the copper takes on the nitrate to form copper nitrates. And the hydrogen is joined up with the free nitrate. I mean to form water. Okay, so the most important thing is that the copper is actually taken on here. It obviously has a charge of zero. And here it has a charge of plus two. And it's joined up with the nitrate. Right, so that is a redox reaction. Great turns. I hope that you have learned about all the different types of ion exchange reactions. I hope that you have taken them on board. Please go and learn them. Understand what each of them is meant. What is meant by each of them. Thank you. Have a great day.