Volumetric Instruments - Video Tutorials & Practice Problems
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Volumetric Instruments
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Laboratory Materials 1
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in this video, we're gonna familiarize ourselves with some of the instruments used in a basic chemistry laboratory. Now we're going to say here that the laboratory portion of your chemistry course puts into practice some of the concepts you'll gradually be learning this semester. So you're gonna be learning about trey shins as well as dilutions as well as other concepts such as evaporation. And with these concepts comes the use of instruments or apparatus is that help us to do these types of processes. So here we're gonna take a look at each apparatus and learn its name and its basic function. So for the first one we have in this image we have what's called a transfer pipette. So these are your basic um pipettes made out of plastic, cheap plastic. We use them from the name. You can tell they're used to transfer small amounts of liquid. Typically will transfer some of our solution maybe into another container. And then we'll quickly dispose of the transfer pipette in the indicated waistbands within your lab. So here, its primary use is just to transfer small amounts of liquid. Now here, in this next image, this is what is called ARB. You're it. Okay, so it's gonna become important that you guys understand how to use a pure it. You're gonna pour in your liquid into the top of the bure it. The liquid that you're pouring in is called the tight Trent. And here, let's say that this mark here represents 25 mls. So we've placed in 25 ml of our tight trend. And as we start and we open it up here with this stop cock here which opens up the valve and lets the tightrope pour out. And as it's decreasing down, you're counting how much of these titans you're using. So if we stop and we see that we've reached this point which is 18 mls, all you do is you subtract these two numbers to know how much of your titrate you used. So then you used seven mls. So to go drop by drop within a container that has another solution. So we're gonna say here that this is typically used in the preparation of solutions. And you're commonly hear being used a lot when it comes to acid base titrate, asians. Okay, so those are the predominant times that we use the burek. Next we have here, this is a funnel, but it's more commonly known specifically known as the Buckner funnel. So here we have these little openings here, these little holes. And what you're gonna do here is you're gonna place on it, filter paper. Okay, so you're gonna take this filter paper and basically put it on top here where it covers up these holes. And then what's gonna happen is you're gonna have a container with liquid in it and in this liquid you have bits of solid material that hasn't dissolved. And you're gonna pour it into this Buckner funnel. The liquid portion will pass through the filter paper through the holes and drip out here into some type of container. The solid portions are too big to fit through the holes so the deposit themselves here. And as you can see, this Buckner funnel is really used to separate a solid from a liquid. Okay, so we're separating a solid from a liquid. We're gonna say that this process can also be called filtration. You're filtering out the solids from the liquid. Now we're gonna say here that this buck will funnel typically goes with this vacuum flask. Okay, so there's a lot of names you might hear for, but it's mainly a vacuum flask because right here in this opening here, we would attach a hose which is connected to a vacuum and turn on the vacuum and it would start to suck air out. And imagine that this Buckner funnel is on top here, not the best drawer. So it's sucking out the air and what that causes it causes the liquid to drip up faster so that you'll be left with the solid particles on the filter paper within the But no funnel. So here, this vacuum flask, it aids the Buckner funnel infiltration. So that's its primary purpose. Next. As you can see there's a lot of different instruments, they're very similar but somewhat different from one another. So, what we have Next here is a graduated cylinder. Typically in your lab, you'll have a small one, which is 10 mls and you'll probably have a larger one which could go up to 100 mls. Okay, those are the two standard size that you're typically going to see in your chemistry lab here. All they help us to do is measure out volumes. Okay, so they're not very precise, they're just helping us to figure out um 10 mls or 100 mls in terms of amount of liquid that we have. What we have next here is we have our beaker. Okay, so this is just helping us to measure out larger quantities of liquid. We're gonna say the typical size that you'll find in your lab are 250 mls of this or maybe even 500 mls. Now, next, what we have here is we have a volumetric flask. Now this is used for dilution. So what we do here is we have our solution here and here these things are typically 100 mls in size but there are larger ones that can go up to like one liter. So this is our solution here. And let's say our solution is 25 MS. And here we say that it has a concentration. Now we're talking about terms that you might not have covered yet, but eventually we'll get there. So we have a solution that's 25 mls in volume and its concentration is 250.10 moller here, we're gonna dilute it. And diluting means that we're gonna add water to it and we're gonna add enough water to reach the line here and we'll say that that mark there is 100 amounts. So I'm gonna fill it up with water right all the way up to the mark. And when you're doing dilution with a volumetric flask, make sure you mix it thoroughly, shake it up and down so it mixes thoroughly. So so that way what's on the bottom is allowed to reach the top and then back down so that you get a thorough mix throughout and here when it comes to dilution, we use a dilution formula which is M one V one equals M two. V two. M one represents our initial concentration or polarity volume, this is our initial volume And then M2 represents our final volume or final polarity or concentration or our diluted concentration And then V two represents our final volume. V two, which is our final volume equals your v initial plus the volume added. So in this case We had 0.10 moller of concentration of our solution, Its initial volume was 25 MLS here, we don't know what it's new concentration will be, but it's new. Final volume is 100 mls. Once we've added all the water we needed and all we do is we divide both sides by 100 and you'll be able to find out what your new concentration would be for your solution. So that's the approach that we take in terms of of a dilution question later on, if you guys haven't done this yet, we'll see within our chapter reviews, how do we approach dilution questions. This is just a basic premise in terms of how do we set it up? But remember to do dilutions within the lab, we use a volumetric flask. And then finally here we have what's called another type of flask. This is an airline Meyer flask. Okay, so basically here this is similar to a beaker in that we have it in terms of measuring out amounts of solution. But this one here is really to transfer transfer larger amounts of solution. So let's say you could have measured out. So in terms of the processes, we could have done a lot of things, we could have used the bureau to measure the amount of solution. We could have used a bucknell fun on a vacuum flask in order to isolate the liquid portion and get rid of the impurities which are solids. We could have then taken that solution that we isolated and put it in the volumetric flask and dilute it with water and that amount of water that we're adding to it. We could have measured with either the graduated cylinder or the beaker. Once we've created our solution we could have transferred it finally to this early Mayer flask at the end. And if we wanted, we could further dilute that larger amount of solution. All these things work together in terms of volume manipulation and recording again, it's important that you guys remember the names of these instruments within your lab because your Tv or your professor may just say the name of the instrument. If you don't know which one they are, then you'll have a hard time. I'm setting up your lab again. This will go hand in hand when you go and cover solution cam mystery when we start talking about polarity and moles and grants and terms like that. We'll continue our discussion on other instruments found within the lab later on in an additional video. But for now just keep in mind what each one of these instruments are called and what their primary functions are.
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Laboratory Materials 2
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in this video, we continue our discussion of laboratory instruments and their use within our basic chemistry laboratory. So here we're gonna say, we're gonna continue with the discussion, we're still gonna look at solutions and the transferring of them were also going to pay closer attention to solids and their use and instruments needed for them within the chemistry laboratory. So in the first image, what we have here is we have what's called a crucible, which is the container and its lead. Now within your basic chemistry laboratory we have these large ovens. These ovens can reach temperatures in the several hundreds of degrees. Basically what we do here is we take our wet sample and we place it in the oven. Usually wait until the next following lab until it's completely dried out. So here are crucible we're gonna say is used to heat small amounts of solid material at high temperatures. Now we're gonna say here that when our substance is wet, we're gonna say that it's hydrated. And once you put it in the crucible and then place that within the oven and give it enough time, it'll dry out. All the water will be driven out of the out of the substance. And what we'll have left is something that is completely dry. And when we say that a substance is completely dry, we call it anhydrous. Okay, so this would be our dry sample and this is when it's wet. Now similar to a crucible is we have here an evaporating dish or an evaporation dish. In this case we don't use an oven in order to heat our our hydrated substance. What we do here is we just place some liquid on this dish and give it time to evaporate, leaving behind a solid. So this here is just used two contain a small amount of liquid um so that it can undergo evaporation, it undergoes evaporation. And remember the whole point of this is to leave behind a solid. Now, the next two objects here we have our spatulas and here we're gonna say that this is a scoop. So spatulas when we're trying to take a small amount of powdered solid um from a container within your lab and maybe place it within a beaker or a flask. So this just helps us to transfer small amounts of solid, usually in powdered form. And as scuba lies just to help us to transfer larger amounts of solid. Next what we have here is our basic funnel. Remember we've seen a Buckner funnel earlier, which is used in vacuum filtration here. This is just a regular funnel. Now it's primary uses. So basically it helps us to transfer liquids or solids if they're in powdered form or or small enough into a container with a small opening. Right? So in this case, all it's helping us to do is stop spillage because it's hard to transfer a liquid from a bottle into a flask with a small opening. So we use a funnel to help us, we just poured into the funnel and we make sure that as much of it as possible gets within that flask. Another method that we can have with this is if we use filter paper, so within lab they'll teach you how to fold a filter, a piece of filter paper. So basically your filter paper is circular like this and what you do is first you fold it in half and then you'd fold that half and half as well, so you have that and then you would hold it out like this and just put your hand through it and open it up and it would form basically like a porous membrane and you place that within the funnel and then you can pour a liquid through there. And what would happen here is the liquid portion would drip out of the filter paper into the flask and what will be left behind would be some solid that's solid sometimes refer to it as a residue. So if filter paper is used, it can be used two separate a liquid which is our Phil trait and a solid which is our residue. Now, finally, what we have here our last image. This is also a funnel, but it's different from a Buckner funnel which is typically used for vacuum filtration. It's different from a regular funnel which is used for simple filtration or just the transferring of liquids or solids into a container with a smaller opening. This is a separate story funnel or separating funnel and the whole purpose of this separate story funnel. It basically helps us to see. It helps with the separation of a liquid and a solid by exposing the solid to another solvent. We tend to call this partitioning and we'll talk about this later on. We typically see this when we're doing acid base extractions. So we'll talk in greater detail about what exactly is an acid base extraction and how exactly is the secretary funnel use when doing this type of process. So these cover a majority of the basic instruments that you should be exposed to at some point within a chemistry lab. So it's important to know what they look like and their main purpose. Again, laboratories are a lot of work. I know and you don't get as many credits for it, but it is taking into practice some of the concepts you're learning in class and bringing them into a real real world setting. So just follow what your professor says or your ta says within the lab. Always be careful when transferring of any liquids or solutions. Follow all the rules study. You should be able to do well within your lab.
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example
Laboratory Materials
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now that we've gone over some of the basic lab instruments that you're gonna see within the chemistry laboratory, Let's see if we can answer some of these example questions. So for this first one it says if a scientist wishes um to measure out exactly 25 ml of a 250.100 Mueller hcl solution and added 2.200 lower end a weight solution. Which instrument would be most useful at this point. We've talked about basically all of these different instruments, but the one that we haven't talked about is option B, which is the sucks let extractor. Now let's not worry about the whole sucks. Let extractive portion. That's just a specific type of the extractor. Let's focus on what do extractors do extractors are built into a process called distillation. And like all other extractors within distillation, they're used to help separate liquid liquid mixtures. So you have two liquids mixed together in a solution and you want to be able to separate them. What you do here is you vaporize the liquid solution so you apply heat to it. One of the liquids will be easier to vaporize than the other. The one that's easier to vaporize it will become a gas much faster. You collect that gas portion and then once you've collected enough of that gas, you cool it down into a liquid and in that way the part that vaporized sooner becomes a gas and then we separate it into its own separate liquid mixture. So at the end you'll have two different liquids separated from one another. But here they're asking us not to separate liquids. They're asking us to measure out exact amounts of these two solutions. So this would not work. And the image below is the basic image of a sex like extractor. We'll talk more about distillation later on. Next we have a transfer pipette. Now transfer pipette. We have a graduated cylinder. We have a volumetric flask and we have a bureau. Now all of these deal with measuring out a quantity of the liquid. But in the question they're saying which one will measure out exactly 25 ml of 250.100 moller Hcl because they say the word exactly. That means we need precision. So precision is needed. A transfer pipette would not work because that just helps us to transfer a small amount of the liquid. We're not really measuring how much of that liquid we're transferring so it wouldn't work. A graduated cylinder is to help us transfer larger amounts of liquid here, we only need 25 ml so it wouldn't be ideal. A volumetric flask. Remember that This is useful when it comes to dilution. Not when it comes to precise transferring of liquids. The best answer here would have to be our Burek Bure ETS are great when it comes to the preparation of solutions like I said earlier on. And they're commonly used in acid based hit rations. So our bureau right here would be the best choice if you don't quite remember what each of these instruments look look like, make sure you go back and take a look at the images that we talked about with each one of these instruments now that we've attempted this one. Let's see if you guys can attempt the next example one, you might not know how to approach a question like this just yet. So if you don't, don't worry, just come back and take a look at the next example video where I go over, how do we approach a question dealing with a dilution within the lab?
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Laboratory Materials
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what is the polarity of a solution made by mixing 200 mls of pure water with 100 mls of 1000.75 molar potassium chloride solution. Alright, so anytime we're adding water to any type of solution, that means that we are doing a dilution. So remember a dilution. Is any time we're adding mixing or tight trading with water. And when it comes to dilution we use the dilution formula which is M one V one equals M two V two. So they're asking us what is the polarity after we've added this water? So they're asking me what is M. 2? The word of means multiply, Which makes sense because this would be my M1. This would be my v. one. They're multiplying each other. We don't know what M2 is now V two equals our final volume and our final volume equals the volume. Initially that we had plus the volume of added water. So initially we started out with 100 mls right here, 100 mls. And what did we do to that? 100 mls, while we added an additional 200 mls of water. So that means my final volume or V two is 300 mls. So all we have to do now is solve for M2. So divide both sides by 300 MLS. So it would just be .75 divided by three. So my new polarity would be 0.25 molar giving me option B is the correct choice. So remember in a dilution, your new concentration or polarity which is M two is always smaller than your M. One. So this is just a basic dilution question where we have to use the dilution formula. Continue with this idea of dilution. Let's see if you guys can figure out how to answer example three. Once again if you get stuck and don't know where to go, just come back and take a look at the next example video where I go over how to approach this very question.
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Laboratory Materials
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So for a final example question on this page we're gonna deal with a dilution. Now it's one thing to just use the dilution equation to solve within a classroom, but it's another thing when you're in the lab and asked to do a dilution yourself. Dilution can be a bit tricky. So the approach you wanna take is this so we want to create 100 fold dilution. Okay, so just remember in a dilution that means that our solvent will have to be larger than our solution. Okay, so we have to put that out there first. So knowing this, we know that they won't work because in a the solvent is less than our solution. So that's not gonna work. And when it comes to a dilution they want us to do 100 fold dilution, that means it's gonna be a ratio of 100 to 1. But what exactly is the 100 referring to? And what exactly is the one referring to When it comes to a dilution, we're gonna say here it is, the solvent plus solution and its ratio to the amount of solution. Okay, so that's what the 100 to 1 is referring to. 100 fold dilution is 100 to 1, meaning we have 100 when it comes to adding up the amount of solvent and solution together compared to one for the solution. So here we know that a is out. So if we take a look at the other options, what do we have for b? We have 90 and 10. So this would be 90 plus 10 And then this would be 10th. So that would total up to 100 to 10. And this would represent a if you divide both by 10, this would represent a 10-1 dilution or a 10-fold dilution, which is not what we want. Next for C we have 99 parts solvent plus one part solution solution. So that would be 99 plus one And then one. So that would be 100-1. This would represent our 100 fold dilution. If we take a look at the last ones here, we have 100 plus 1 to 1 that B one a 1 to 1, not quite what we want. This would be 100 and one full dilution which is not what we want. And then the last one would be 10 plus 1 to 1. So that would be 11 to 1. So this would be an 11 fold dilution. So here, just remember a dilution when it comes to the ratio it's the amount of solvent plus solution in ratio to the amount of solution. Hundredfold would mean that we have 100 when it comes to the amount of solvent and solution together compared to the just the amount of the solution