all right guys reactions of metal ions in aqueous solution by the end of this video you're going to know every single color change observation and equation you need to know for this topic under AQA a level chemistry okay so what exactly do we need to know this is straight out of the specification you need to know the observations and the equations for the simple test tube reactions of the following ions with the bases oh minus so hydroxide NH3 and carbonate so NH3 is ammonia now there's two oxidation state charges of these metal ions okay you're going to have two plus and three plus now AQA have made this pretty easy for us and there's only two different metal ions for each okay so for the two plus charge ions you have iron and copper and then for the three plus you have aluminum and iron okay so let's start with the four aqueous ions you need to know these are going to be in the form of hexa Aqua complexes okay and we're going to look at what colors they have to begin with these are all going to be Solutions okay if something is aqueous it's a solution so let's look at the form that we're dealing with and look at the equations that occur and the color changes so let's look at Copper two plus to begin with okay so you're always going to have this same format where you have the metal right here then you're going to have six water molecules these are the ligands square brackets to denote a complex and then the charge of the central metal Ion at the top right okay now this can change this this charge right here if you're dealing with a negative ion for example a chloride ion this is going to change the overall charge on the complex but for the sake of this we're only dealing with starting water molecules okay and these are all neutral so we completely fine here so this will give away what the charge on the central metal ion is to begin with all right guys so I've drawn off four different complexes out our hexa Aqua complexes what are the starting solution colors so for copper two plus right here this is a blue solution okay what is our iron two plus this is a Green Solution okay what is our iron three plus this is a purple or Violet solution the fourth one here aluminum three plus this is a colorless solution okay I'm going to use black here because I don't have a colorless pen color but hopefully that's all good for you guys now we've done the colors let's look at the equations that occurs first off I'm going to look at when we react with hydroxide and ammonia okay these are the first bases that we're going to look at and then we'll move on to the carbonates afterwards so let's start with copper here when we're reacting it with a hydroxide you just literally just do plus o h minus here to signify the hydroxide ion now in questions for AQA you're normally going to be reacting with sodium hydroxide so just keep that in mind but we're only dealing with the ionic hydroxide portion of this compound okay so it's real simple here now something you want to keep in mind that makes these equations so much easier to remember is whatever the charge is on the metal ion so for example this copper it's two plus you just Chuck a mole coefficient of that charge in front of the hydroxide ion okay and it's exactly the same for ammonia which we'll look at afterwards but just remember that tip and it will save you quite a lot of time and you won't have to be super stressed out remembering all the different equations so what is this form then this is going to form a precipitate okay and this precipitate involves four water molecules and two hydroxide molecules okay and this is a solid you have to show this as a solid and that's something I've actually left out so all of these hexa Aqua complexes here are aqueous okay and when they react with the hydroxide or the ammonia these are also going to be aqueous so just keep that in mind both of our reactants here are aqueous whereas we're going to have a solid precipitate product forming what is our other products we get two water molecules kicked off so I'm just going to write that right here to H2O and this is a liquid okay just lowercase L right here okay so I've drawn out our iron two plus equation as well as you can see here these are exactly the same all you have to do is swap out what the metal ion is okay now these first two color changes are super easy so as I mentioned our starting solution is blue for the copper and green for the iron right super easy one here this forms a blue precipitate and a green precipitate respectively okay so these first two ones are super easy you just have to remember the exact same color but they just form a precipitate rather than remaining as a solution okay so let's quickly move on to our three plus ions here now I'm not going to spend too much time explaining things here but just remember my tip from before if it's a three plus ion how many moles of a hydroxide are we going to be reacting with three okay simple as that so both of these for the iron and the aluminum is going to be three oh minus and the main difference here for these two three plus ions is instead of it being four molecules of H2O and two oh minuses or two hydroxide right here it's going to be three of each okay so it's going to be Fe h2o3 and then oh three okay and again this is a precipitate so really keep that change in state in mind all right so what is our color change going to be as I said Iron three plus this is originally a violet or a purple solution so I'm just going to put purple here but Violet is also fine and what is this going to form it's going to form a precipitate again as we can see with this solid state symbol but it's going to be brown okay Brown precipitate okay just keep that in mind goes from purple to Brown next up was our aluminum so this started with a colorless solution and this actually forms a white precipitate so I'm going to write that out in Gray but just remember white precipitate okay so we've looked at what occurs when you react with a hydroxide you also need to know ammonia okay this is super simple what we're going to do here is you keep the mole coefficients the same but literally just swap it out with NH3 the product right here these this first row of products is exactly the same but the water molecule is going to be changed for an ammonium ion so in nh4 plus I'll write that out quickly and this has to change to aqueous okay the state symbol is no longer an L or a liquid for water it's going to be aqueous for the ammonium ion okay okay so I've written it all out and you can see here that the mole coefficients stay the same two for a two plus three for a three plus and then we're going to get ammonium ion aqueous forming here instead of water now the precipitates that are formed exactly the same and the colors are exactly the same so you don't need to worry about that now a little bit of extra information here if they ask you what type of reaction this is it's going to be an acid-base reaction now in a level chemistry you have two different types of acids and bases you're going to have a bronson-lowry acid base or a Lewis acid base and these are Bronsted-Lowry acid-base reactions or deprotonation acid-base reactions as you can see here this ammonia molecule as well as the hydroxide ion gains a proton from this water ligand right here okay so what happens is this acts as a base accepts a proton from the water ligand which ultimately acts as an acid and it's deprotonated right here which you can see that is left with an o h instead of a H2O okay so a little bit of extra information there hopefully that helps you guys out okay something that can really trip students up is when they ask for excess hydroxide or ammonia okay now the color changes and the equations that I just run through these are specifically for limited amounts of hydroxide and ammonia now AQA is not always explicitly clear of this they may just say add sodium hydroxide or something like this they may not say limited amounts whereas if they say excess this is explicitly clear that an excess amount of the reagent has been added so just keep these slight caveats in mind now there's two we need to be aware of for excess hydroxide ions we're going to be dealing with aluminum three plus more specifically the product precipitate once it's already been reacted with the hydroxide and then a copper two plus precipitate once it's reacted with ammonia and I'll go through these right now so cast your mind back to the previous equation and think to yourself what was the aluminum three plus precipitate that was formed when reacting with a hydroxide okay so it was aluminum h2o3 oh3 remember the state of this is solid okay and when we react with excess hydroxide you simply add one more mole of hydroxide like this and this is going to be aqueous okay and we're actually going to form a complex here what is our complex going to be it's going to be aluminum o h four of these guys and we're going to have a one minus charge remember earlier I said when we're adding in negative ions for example like a chloride ion or an o h minus ion this is going to alter the overall charge on the complex Okay so we've got one aluminum three plus right here and then we've got four lots of oh minus so that's minus four right here and this gives us an overall charge of -1 so just keep that in mind so what is the state on this complex is going to be aqueous okay all complexes are aqueous just try and remember that and then we're going to have three water molecules kicked off again this is a liquid right here so what is the observation going to be here it's going to be this precipitate right here what color is this precipitate do you remember it was white okay White's precipitate and the observation is that this white precipitate dissolves to become a colorless solution again okay even though it's a different starting complex this isn't our hexa Aqua complex it's still a colorless solution so I'll write that right here colorless solution okay now a little piece of extra information that you really need to be aware of that they can chuck in for like a quick one two mark question is the fact that this right here is amphoteric what does amphoteric mean let's break this down some of you may already know it simply means that it can react and dissolve in both acids and bases all right okay just remember that this right here can react with both acids and bases so what's the equation you need to know for if it reacts with an acid instead of a hydroxide they may ask you this okay so it's going to be our starting reactant exactly the same now instead of reacting with one mole of hydroxide ions we're going to react with three moles of protons so from an acid right here and this is going to be aqueous it's going to be a solution of acid and this is going to form what is it going to form hexa Aqua complex okay we're going back to our starting reactant h2o6 3 plus and this is aqueous okay hexa Aqua complex right here so we're going from a white precipitate to a colorless solution so you're going to get the same observation each time but just keep in mind the change in the other reactant right here for these two equations and remember the keyword amphoteric okay right that's aluminum three plus out of the weight let's look at Copper okay so when we're reacting copper with an excess reagent you don't need to know about hydroxide in excess but you do need to know ammonia in excess okay so if we write out our starting precipitate right here oh2 and this is a solid what do we react this with we react it with an excess of ammonia and this one's kind of one you just have to remember you're not going to be dealing with two moles of ammonia for the two plus copper ion we're dealing with four moles of ammonia okay and this is aqueous just try and remember that what is our product going to be now we're going to have a complex forming okay I'll go through that complex in a second and you're going to have two other products okay so our complex is going to be a copper two plus and it's going to have four ammonia ligands and two water ligands okay two plus charge still the same because ammonia and water are neutral so it doesn't affect the overall charge this is going to be aqueous remember all complexes are aqueous we're going to have two moles of water liquid and two moles of hydroxide aqueous okay as we can see here two moles of water were kicked off and we're only left with two here and then these two moles of hydroxide were also kicked off and replaced with ammonia now what is the name of this equation or reaction I should say it's a ligand substitution okay and you really need to know this what is the color change going to be what was the color change of our starting precipitate do you remember kind of cheated for you and wrote it out with the font color but it's blue okay we've got a blue precipitate here and what is our resultant complex going to be what is the color here it's a deep blue solution sort of throwing you off with a green here but it's a deep blue solution now what would we refer to this reaction as yes it's a ligand substitution reaction but we would not normally get this forming if it was a complete ligand substitution reaction you would just get six ammonia ions right six ammonia ligands I should say whereas this is referred to as incomplete ligand substitution okay or partial ligand substitution I would stick with incomplete but partial is also fine now you also need to know what the ammonia acts as in this reaction and it acts as a Lewis base okay what is a Lewis base it's an electron pair donor so essentially it's a ligand you can think of it as a ligand but it donates an electron pair onto the central copper two plus and forms this aqueous complex right our last base here that we need to react with carbonates okay so the two plus ions are going to react slightly different to the three plus ions in terms of the products so let's look at the two plus to begin with and then we'll break down the three plus ions separately afterwards and look at What observations and color changes you need to be aware of okay so the first thing to remember here is when we're reacting it with carbonates with a two plus metal ion there's only one mole of carbonate required in the equation and so this is just one thing to remember here slightly different to ammonia and hydroxide ions where you match the transition metal charge to the mole coefficient we don't do that here it's just one mole of carbonate ions okay CO3 two minus now the standard carbonate that you're going to see in questions is sodium carbonate na2co3 that's a standard one you're going to be reacting with but for the sake of the equations just show the ion co32 minus so what's going to form here we're going to go from an aqueous complex to a precipitate okay what precipitates are we forming for the two plus ions we're going to be forming a copper carbonate okay and this is a solid and water molecules okay six of these guys are kicked off this is a liquid okay and I'm going to draw out the exact same thing for iron okay iron carbonate real easy stuff here guys solid plus six H2O now I haven't properly matched the colors to the the ink color of my pen here but hopefully it's going to be completely fine for you guys copper carbonate what color is this precipitate it is a blue green color Okay blue green precipitate so very similar we're going from an aqueous solution which is what was this you guys remember what this was blue okay blue to a blue green precipitate okay now what was our ion two Plus Solution starting color do you remember it was green okay so going from a Green Solution what precipitate do we have here for the feco3 green okay real easy one so I suppose when in doubt with I and two plus you can kind of just put green on the page and hope for the best um but just keep in mind that you have to say whether it's a solution or precipitate otherwise you will not get the mark okay so what are these reactions referred to you do need to know this okay these are called precipitation reactions okay so let's move on to the three plus ions how do these differ just do your best to remember that for the three plus ions these are not formed okay the solid metal carbonate is not formed okay we get a different product here so let's go through these right now okay so I've drawn out our starting hexa Aqua complexes for our three plus metal ions really important stuff you need to keep in mind the mole coefficients completely switch up okay so you always need to put two in front of these starting complexes for the three plus reactions with carbonates and our carbonate ion is no longer one mole okay we need to react it with three moles right here CO3 two minus three moles of that this is aqueous remember and exactly the same thing for our aluminum three plus okay and we're going to get three products formed here so hopefully I have space for this the first product here is going to be exactly the same as the products we formed when we were dealing with reacting with a limited amount or just simply sodium hydroxide and ammonia okay so it's going to be h2o3 oh three okay and this is a solid precipitate now we're also going to do the exactly the same thing for aluminum h2o3 oh three okay now you need to know the color changes that are occurring here you also need to know a secondary observation that is really important to remember what is that going to be is going to be the other product that is formed okay what is that product some of you may already know based on the fact that we have a missing carbon here and an oxygen it's going to be CO2 okay we get three moles of CO2 forming what is the state of this CO2 is obviously a gas right and you're going to get effervescence forming here so I'll write that out in a second let's complete this one not sure what happened to the three there three CO2 gas and we also have water forming okay three moles of water let's draw that underneath all right so we've written out our equations in four I left off the solid state sign there so let me put that there state symbol what are our color changes do you remember what iron III plus started as it was purple okay purple or Violet solution all right and what are we forming here Brown precipitate okay exactly the same as the hydroxide and ammonium precipitate formed so Brown precipitate okay now do you remember the aluminum and the aluminum precipitate that forms colorless solution if you guys remember that and we actually write down solution here and solution here and this is a white precipitate White precipitate okay cool now as I mentioned we have a secondary observation here effervescence okay this carbon dioxide is going to Bubble Up through the solution and we're going to get effervescence so f s let's run out of space but hopefully that's all good there F of essence really try to remember this for these three plus reactions with carbonates all right guys so that's all the observations and equations you need to know but this is a perfect opportunity to use some active recall take what you just learned rack your brain and apply it to three very simple questions here just to test yourself just to get some good Revision in so question one what is the observation when you react an aqueous aluminum 3 complex with sodium hydroxide question two what is the equation for when you react an aqueous Iron III complex with a carbonate solution and what is the color change and the equation for when you react copper II and its precipitate with excess NH3 thank you okay observation here what was our aluminum III complex starting color and State it was a colorless solution and what is our product what is our precipitate formed it's going to be a white precipitate okay all right now for this answer here I would simply just say a white precipitate is formed or you can say colorless solution forms white precipitate something along those lines that will be completely fine but I would simply say white precipitate formed or produced something along those lines now you may be thinking this is unfair he didn't say whether it's a limited or excess amount of sodium hydroxide as I mentioned guys AQA is not always going to specify that it's limiting okay as long as they don't say excess assume that it's limited all right and just remember those equations all right question two what did you get here all right this is our equation here two moles of this hexa Aqua iron three plus complex three moles of carbonate ions forms this precipitate right here three moles of carbon dioxide gas and three moles of water I didn't ask for the observation just the equation here just really keep in mind these moles that pop up okay so two moles of the complex three moles of the carbonate two moles of the precipitate three moles of carbon dioxide and then three moles of water okay try and remember that and you'll be completely fine so last one then question three color change and equation this time for copper two plus with excess ammonia all right so I've written out the equation here guys four moles of NH3 this is the excess equation you need to remember and we're starting with our precipitate okay we're not starting with our Hector Aqua complex we're starting with our precipitate right here a solid and we're forming this complex right here okay so what is our observation where is our color change going to be do you remember what this precipitate color was real easy one blue okay blue precipitate and what is the color of our solution is it simply blue solution no deep blue or dark blue solution okay just remember that and you'll be completely fine so with that guys that's the end of the video keep revising memorize the color changes and the equations hopefully it's not too difficult for you guys if you learn something if you found this video helpful and you want to see more content just like this like the video it really helps the channel grow best of luck with your revision and upcoming exams guys until next time peace