Reaction Mechanisms Activation Energy Lecture 2 3 16

all right good morning welcome back hopefully you made really nice snowman made giant one that makes my never made my life but he was like ya know ten or twelve feet tall the base was like this big it was awesome Priscilla and my kids took picture with it making it look like they made it okay we have good time with it so today everything's messed up and we're gonna try to correct things so we should have known something we're gonna talk about just couple simple things because this hour an hour shorten as well you got to talk about lab as well with that couple congratulations go out to and had to do little finagling here because certain groups weren't the size they were supposed to be and other things like that ester lab there's actually tiebreaker there's many people tried but unfortunately there's one group that had like nine people having all the exact same answers so that would have worked out very well said that you're supposed to keep it individual in smaller groups so when nine people all have the exact same seven guesses it that can't be the tiebreaker when it's tied so congratulations it will be going on in trophy eventually to Miranda Jenna and drew they won the Esther fly out they had the most correct which was total of three then pennyworth and kind of make decision on this because this was supposed to only be two-person group and this was four-person but two of these people were in the ester lab so the winner of the penny war is with three hundred and sixty-three drops was Erika and Emily so congratulations pretty exciting all right today we're gonna talk let's make sure we get enough time on this all right reaction mechanisms just two things we're talking about today we're gonna do couple demos as well so it should be kind of fun why don't you have seen before but I've never heard anybody complain less Union again so reaction mechanism you've heard of people saying like the mechanism it causes something to occur reaction mechanism is really unique thing to kinetics but to all of chemistry it's series of steps and today there's not actually lot of notes already more drawings and in drawing out some reactions but reaction might look really simple like we do all through first-year chem here balance an equation first-year come today those learning how to balance today here here's an equation but is that really all the chemistry that's happening so equation doesn't show all the details on what actually takes place and the extra thing is we may not know all the extra chemistry we still have to take kind of guess on it so here's an example and would have written it right here at e^x for an example you got nitrogen dioxide in your axe of carbon monoxide and it just makes and we're gonna do one in second as well nitrogen monoxide and carbon diet it's great but that's actually not the chemistry there are extra things going up and your job is not going to be necessarily coming up with the steps it's your job to interpret these steps say that again you won't always have to come up with the steps your jobs more about interpreting the steps that are given to you because there could be stuff sitting we still don't know about or other things that are happening so here is an example of this it actually happens in two steps and don't expect you to look at that overall and go well naturally those are the two steps and it will break this down more but due to time again I'm having to kind of give you some bigger pieces of information and into it so much so if you're looking at this and maybe you're not thinking this but maybe something clicks and goes well that looks like Isis logging you like can add up equations to make up one overall equation that's yeah it kind of is like that we can take multiple equations add them all together and what happens is certain things cancel now for just what's one compound that is not existent in my overall that you see what's one 1003 right does in no.3 here it doesn't show up here anything else is there anything else in there seals right there one of the end of chooses cross so that's kind of trick question right it's like it's already there well there are ones though that do get canceled out from one side the other and then there's other ones that get cancelled out but kind of in different fashion what am saying saying like this compound was kind of introduced and then it was consumed this one was created and then consumed in different manner but they both cancel out these are two huge vocab words and know you've probably heard of one of / but probably not both catalysts I'm hoping you've heard of that before it's specie as the speed up reaction and it's the yellow one so you might want to draw an arrow actually it's introduced you have to bring catalyst to the party you have to brand cattles to the reaction the other one's called an intermediate it's not even fancy sounding name all really mean it it's descriptive in what it's saying no it's an intermediate in between the equations but the difference is this one's formed then consumed ok so then in parentheses kind of wrote think the big thing you're looking for catalyst is introduced an intermediate it's created right absolutely have that we are gonna talk about one of my favorite reactions you've seen it during chemistry but it's the rope see it's decomposition of hydrogen peroxide it's the only other example we have on here and then we'll get into our topic but it's really not that exciting you just watch the composition of hydrogen peroxide have to wear gloves this is thirty eight thirty percent hydrogen peroxide what you have your house is three percent if this gets on my skin it will turn it extremely white I've never had this happen had colleague have have it happen to them once why's any no and they could barely speak because it hurts so much I'm afraid of becoming all out at once it's all in the groups okay every morning actually lot more good alright so if just have it sit here or I'm gonna put it right here right now it's decomposing why isn't it brown Bob do the murmurs and whispers sunlight UV can break it down so it can decompose it has shelf life it doesn't have tag on here right now but it's shelf like poor if kept this in the this way I'm also using it in the storage room for the next year it wouldn't really be that effective anymore so it does break down it does decompose into water and oxygen so really not much there and much to react later but we could add catalyst and we could speed this thing up Thanks so we can go from that compound to water and oxygen just faster I'm still going to do the exact same reaction from start to finish but there's lot of unseen things that maybe could have happened so what am going to do is I'm going to add catalyst oops oops oops so what I'd like you to do right now is I'd like you to label either put like or knife or intermediate or catalyst what is my intermediate and what is my catalyst now they don't both have to be present say that again you do not need catalyst and an intermediate if ever asked to identify if anything is present you have to be aware you're just looking for what is cancel of and how was it how did it come to be in the reaction and and how does it cancel out so it matters the order if flip equation one equation to it then that changes what was introduced in what was created so what is my catalyst iodine have potassium iodine right here well that is my catalyst that's gonna speed this thing up lot but to make it little more fun want to trap the oxygen so I'm gonna put some soap in there that's the only reason why that's in there and let me shake that up oops can't do that anymore just put that in me are you impressive alright we'll just hope it makes us yay open three three it's heavy comes to mean usually comes out really solid know it's like kind of breaking up but think it starting to break down little bit so that haven't really fast exact same reaction just want you to kind of be aware that like it's the exact same reaction just sped it up the thing is just chalked full of oxygen right now alright so hopefully cross out iodine you cross out owe - for your intermediate okay so that is great example of what catalyst can do for reaction okay I'm just going to leave that there for time all right another thing want to talk about is it's piece of paper so my dad very excited know yeah it's awesome microphone was off to an entire time well that's gonna be the catalyzed pathway that's why reaction goes faster because the pathway is shorter and hope that that makes some sense go yeah like if was on bike this would not take as much time before no no not necessarily like you could have something up higher here is just the pathway would it would lower the activation energy that's also the the peak would be lower okay so all have is one last thing so if we have that drawn okay so we have an equation for this it's in your packet and on kinetics - you should have been working on already so it's it's not something about memorizing it's what have applying know the difference one thing you will notice and want to point the subs is that you have 2 or 1 what you're doing is you're comparing two different reactions of the same type of reaction but at different conditions so right away you can notice that we have ones and twos on temperature in ones and twos on KS so it when change the temperature it changes the rate constant because changing temperatures cause reactions to our molecules and compounds to move faster or slower so reaction can happen faster or slower so if lower the temperature the probably reduces if raise the temperature the increases so you have to have two different conditions because of that we can figure out some different things through this couple things to notice though if for ever reason that you are provided that when you were provided this equation this has 1 you'll notice this will be 2 if this if these flip these just flip so don't allow that to be huge confusion it's still the same thing sometimes what people actually do is is use that to their advantage if they're wanting certain variable wherever they want it like want that on the bottom rail on that on top can just flip those items this is activation energy and that is the that we are given always on our yellow sheets our equation sheets and why know that one have to use is because that one has energy in it that has jewels in it ok so that's what that's about so that is the last of your in local health see everybody what we can so you have and it's kind of gotten little screwed up why did do that with the snow and all that but we have lab dealing with acid rain and some marble statues and I'm not gonna give you lot of insight or there's no procedure whatsoever it's all about you figuring it out yourself and figuring out what you want to do no we were gonna do this in an easier way and was gonna give you all this equipment in the middle of the table so tomorrow that's what you're gonna see in the room it's gonna be all this different stuff that you can choose from lot of it's not useful some of it is and that's gonna be kind of your your choice to figure that out but want to just show you something to kind of get you thinking about this first want you to think about kinetics one and what that means is that we did different experiments to isolate what the rate was how fast things were reacted so if you look I've given you bunch of information that's on this sheet it talks about the challenge so it's your ago it says the challenge your task is to investigate how the speed of chemical reaction between solid calcium carbonate which is lot of what is in marble statue and solution of hydrochloric acid is affected by changing variable relating to the two reactants you will implement the investigation by first constructing and then testing hypothesis so wanted to show you something I'm not measuring anything out like this but here are my two reactants marble chips which will show you right now of course it is and of course you can't see anything so let's turn on the light yes can give you they're like trying to don't need to extend it though you had one whole day off and why you ask well then Nathan asked don't be the voice for them all right so here's the marble chips what I'm going to do we we would weigh them but this is what want to do instead and you would record all that and there's different sized ships and all that good stuff am actually going to now here let me get goggles on I'm gonna use six molar HCl but it doesn't have to be six molar so that's concentration and would measure how much but I'm just going to oops I'm gonna put certain amount it okay what want you to see without me give you know like saying things but just want you to understand that there's things we can measure can you see that kind of it's hard to tell alright I'm gonna put this balloon just so it's weighed on here and now I'm gonna hit zero so zero right now okay what I'm gonna do is I'm gonna put in the marble chips show you couple things this start brainstorming what you need to do it's probably really focused because I'm not gonna help at all they're in the whole lab you need to start figuring out how can you test concentrations that effect rates without changing other things what can you do how can you test these things and there's all sorts of different way so I'm trying to give give away multiple ways that you can test the soap throw the calcium carbonate in there I'm gonna put balloon over this once just to show you and you have the chemical equation maybe this shows you nothing maybe shows you something but if you look you can also see I'm sorry it's kind of look later and if he tell now we feel I'm tracking it's not going as much you should be seen that the mass is dropping the problem is it's only dropping little bit because I'm actually still trapping the gas open that up completely the last me going out lot more would think right so how can test have chips okay have acid how am going to start being able to make table like kinetics one table where can figure out the the different rates can measure rates then can actually calculate them and can figure out the order of this reaction well could all test so have all sorts of different stuff in the middle of table tomorrow on Thursday and you're gonna be able to start looking at it's gonna be bunch of different probes this is gonna be temperature probe of pressure probe there's like for pH probe bunch of different probes like what could you use what what don't you need you have access to balances you have access to diluting and making the acid more concentrate you have access to the chips in any way you'd like how could start testing to figure out rate of reaction of my two reactants and there's only two on your sheet so there's calcium carbonate and there's HCL okay this is the only sheet you're gonna be getting this as post lab so it'll be your jobs start figuring this out no this is the tricky part tomorrow you're gonna be in class with people they may not be in class with you on Friday so if you can kind of see that you might be able to you know kind of brainstorm with them earlier if they're in the Thursday class right away but regardless when we all come together on Friday whoever you're gonna be in with your group you're gonna have to start figuring out okay this is what think we should try to do with this reactants is what think we should try to do with that reactant and let's start to test it it's harder much harder than just giving procedures should we just come in later well you're gonna be done with the tests after pee right if you can make it before but you might have classes on for it your open up for you you're definitely welcome to come in dad's an adjusting class have done so tomorrow's our brains for me I'm looking at it start formulating we're gonna start creating our sheets are also your beginning connects three unfortunately this with snow day had to kind of alter with time and just not enough time they have gotten it done it's very short it's one-sided and all it has to do timer it goes until twenty five that clocks fast no don't remember at that