 In this video we are going to look at the reactions of iron. These will include reactions with air, water, the halogens, acid and displacement. The most common reaction of iron is that with air. You're probably already familiar with the idea of rusting. This results when an iron object reacts with moist air, giving a hydrated iron oxide. Unfortunately this doesn't protect the metal because the iron oxide flakes. What do you think happens next? Pause the video and continue when you're ready. If you said that the new exposed surface forms more rust, you would be correct. The equation for this process is shown in the diagram here. Why if you were to heat the iron in the air? Pause the video and think about what might happen. Continue when you're ready. On heating with oxygen the result is the formation of iron oxides Fe2O3 and Fe3O4 shown by the following equations. What about iron with water? Well this depends. If there is air trapped in the water then as before hydrated iron oxides form rust over time. Iron reacts with moisture and oxygen in the air to form a hydrated oxide known as rust. Iron when reacted with an excess of a halogen that's fluorine, chlorine, bromine and iodine produces iron halides. These have different colors as shown by the equations on the screen. The reaction with iodine is not so successful. This is because iron is very oxidizing and iodine is very reducing. They can be reacted directly but this produces iron II iodide. The reaction again is shown on the screen. Iron will react with acids dilute and concentrated. Can you name any acids that iron might react with? Pause the video and continue when ready. There are a number of possibilities. They include sulfuric acid, phosphoric acid, nitric acid and hydrochloric acid. In dilute concentrations they will produce aqueous iron salts and hydrogen gas. What do you think happens when iron reacts with concentrated acids or if there is oxygen present? Pause think and continue when you're ready. The correct answer is that the iron is oxidized from Fe2 plus to Fe3 plus. In some concentrated acids like nitric acid the surface of the iron forms an oxide layer and stops reacting further. This is not observed with other concentrated acids. The process is called passivation. Iron in its solid state may take place in some displacement reactions. It depends on what metal ion solution it is reacted with. Here's a challenge. Using the reactivity series, what metal ions will be displaced from their counter ions using iron? The correct answer is that iron will displace any of the metals from a solution of its ions if that metal is underneath iron in the reactivity series. So iron will displace tin, lead and copper cations from solutions of their counter ions. In summary, iron reacts with oxygen in the air to form ion oxide commonly known as rust. It may also react with moist air to form a hydrated ion oxide. Iron will not react with air through water but will rust if there is air in the water. Iron reacts with halogens to produce mainly iron free halides. Iron reacts with acid to produce a dissolved metal salt and hydrogen. If the acid is concentrated like nitric acid this passivates the surface so it doesn't react further. And finally, iron will displace a metal from its ions provided they are under iron in the reactivity series.