Writing Ionic Equations

[00:00:00]okay the last little section in this introduction to chemistry is probably the trickiest thing that you're doing this pack and that is called ionic equations the first thing you need to consider is when you take something that is ionic and you put it into a beaker of water so what actually happens from deucesy you'll probably aware that ionic substances when they dissolve in water the ions become free you'll have used this to explain why ionic substances can conduct electricity when they're in water you know the solution the ions in the solid suddenly become free from their crystal lattice free from their structure and can float around and so we've got 13 ions and chloride ions so the first thing we're going to do is just to make sure we understand what I am czar present in each of the following formulas when they're in solution so when I put sodium chloride into a beaker it's made of sodium ions and chloride ions so pause the video see if you can say we chimes are present in each of these it's just working backwards from the formulas to the ions similar to when you were coming up with the formula of the compound see if you can find out the formula of each of these and just tell me the ions yes there we go so ionic substances sodium chloride magnesium bromide potassium and hydroxide ions sodium ions and carbonate ions and then the bottom one just be aware that acids do release their protons their hydrogen ions so sulfuric acid is made of hydrogen ions and sulfate ions so the acid is made of hydrogen ions and sulfate ions because the formula of software I cut it was h2s it's made of two hydrogen ions salsa Italian what ions are present right what about the numbers the stochiometry so often in a balanced equation there's more than one of the thing there so we need to think about now and consider how many are actually present so if I was looking at this formula to NaCl how many actual ions are present of each time so NFC our sodium chloride with the big two in front means that I've got two sodium ions and two chloride ions so have a look for the next one okay what's present in two whole lots of magnesium hydroxide so magnesium hydroxide is made of magnesium ions and hydroxide ions how many hydroxide ions are there in a magnesium hydroxide well in one magnesium hydroxide this one of the 1 magnesium iron and two hydroxides but we've got two so we've got two of these I am turtle we will have four hydroxide ions you'll have two magnesium ions and four hydrops island does look a little bit like I've written for th - oh dude just be careful with your handwriting that's for Oh H minus ions what's present in two sodium carbonate so I've got two lots of sodium carbonate now sodium carbonate contains sodium ions and it has two of those but I've got two lot so - lots of two is four and carbonate items Co 3 2 minus ions and I've got two of those because I've got big two in front to carbonate aliens notice that when you look at these the plotters are - is still balanced I've got four bomb pusses and two two minuses that's fallen far behind three sulfuric acids so every sulfuric acid has got - huge for science but we've got three Lots six H+ ions and every software weak acid has a sort of in it I am we've got three Lots so we've got three sort of eight items this one is for lots of ammonium sulfate so an ammonium ion is an NH part we've got two ammonium ions in our formula but for lots of its lots of two is eight we've got one sulfate I in in half army level we've got lots of sulfates so just be aware that you might need to double up the number of ions present then a couple of other things to watch out for when ionic compounds are solid we know that they're fixed in their lattice so they don't separate into their ions so if we have a solid structure in our formula we're gonna write things like and see ya solid it's not gonna separate into islands and covalent compounds don't even continue now in space there covalent so they're not altered in any way in ionic equation so we'd have things like co2 gas or even CL 2aq even though exact yes an area softer means itself in solution of water now it's still CL - because it's covalent next eh gasps h2o liquid these things aren't gonna separate co2 gas now these things aren't going to separate into items because they're not high on ik they're covalent right so how do you go about writing an ionic creation well you need to decide which things you can separate into ions and which things you can't separate them and then cancel ions that appear on both sigh - Carlos the spectator items it tells us that the top let me get rid of those because they just watch they don't do anything they don't change from beginning to end they spectate and so we're just gonna get rid of those fine there's like a little flow chart questions to ask yourselves so the first question is is it yes and if you say yes start to think about it is it ionic or is it an acid and if it is that on a car and acid you know start splitting it up into ions if it's not tire on a car an acid but it's air Chris white the CL to wake you they just believe it as it is because it's covalent and if it's not in curious you're gonna leave it as it is and just include it so these are some rules they might be worth keeping that page in mind what we're gonna do question number one is the air quiesce yes is it ionic yes because it contains a metal so I'm gonna split it into sodium and hydroxide ions that's the first thing and I'm gonna go into the next part of my question hydrochloric acid it's an aqueous yes second question down the floor chart is it ionic or an acid well hydrochloric acid is an acid so acids get split so it's made of hydrogen ions and chloride ions I'm gonna go on to my next thing sodium chloride is it aqueous yes is it I on it yes cuz it contains a metal also split it and then the last one is it Arius no leave it as it is Rostow anything that's on the same on both sides sodium ions are on both sides na plus exists on both side identically CL minus exists on both sides do anything a necklace together and then you can have a go yourself so is it aqueous yes is it ionic yes because it comes down as a metal so we're going to split it up sodium is that but there's a two other great so there's two sodium's you don't put it after now there's two surgeons under carbonate china for the big two in front of hydrochloric acid so there's two hydrogen ions and to acquiesce and an acid so we're splitting it up to of each part we've got two sodium chloride to sodium ions and chloride ions these two things are not yes all right so we just write them down h2o i'm co2 and then we're gonna cross out anything that's the same on both sides so i've got 230 my hands on both each side I've got two chloride ions on each side so I'm left with Co 3 2 - I'm 2 h + co2 and my spectator ions na+ and cl- now what this tells the chemist later on is this reaction would work exactly the same if I chose to use potassium carbonate and sulfuric acid because the potassium the sodium and the chloride ions they didn't do anything so I could change those to other metals and other non metal ions and it wouldn't affect the reaction because the reaction is the carbonate ions reacting with the acid to make carbon dioxide and water I'll pause the video and we need to have a girl and see if you can come up with ionic equations for each of these three okay so that's all put these then the first one I guess the little trick try and catch you out was that the magnesium carbonate at the start was actually solid and therefore cannot be split into ions because the ions are fixed in the lattice and so we just leave it as mg Co 3 so if something is solid liquid or gas we don't attempt to separate it so mg Co 3 its Energy's still mg Co 3 this time only the chloride ions are spectator ions in the second one we split the silver nitrate we split the sodium chloride but silver chloride is a solid so we don't split that and we can see that silver ions and chloride ions make silver chloride you may be familiar with this reaction you will have done it at GCSE is the test for a chloride iron you add silver nitrate this is this thing here silver nitrate you had this the two solutions react to produce silver klein which was a white precipitate and here I remember that if it had been bromide ions here would have got yellow cream precipitate sorry and if it was iodide and to get a yellow precipitate but I could have used potassium chloride but it's not a test for the sodium it's just a test for the chloride ions and then the bottom one again just watch out for a couple of things just because it's serious doesn't mean its ionic BR 2 where Q is not ionic BR 2 is still covalent it's made of only nonmetals and so BR 2 but sturdy and iodide has got a Mexican nonmetal so we split that the sodium ions are going to cancel and we get BR 2 plus 2 I minus goes to 2 BR - and I - so the redox reaction bromine is stealing the electrons from the iodide ions to become bromide ions bromine is being reduced the iodide ions are being oxidized that's a little section on writing ionic equations this is something you're probably going to need to practice a little bit there's plenty of examples that you can use in your Cox