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GOB Chemistry
Learn the toughest concepts covered in your GOB - General, Organic, and Biological Chemistry class with step-by-step video tutorials and practice problems.
The laboratory portion of your chemistry course puts into practice some of the concepts you’ll gradually be learning. In this section we will familiarize ourselves with some of the basic apparatuses you’ll be using.
Laboratory Materials
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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'll be learning about hydration ins as well as dilutions as well as other concepts such as evaporation. And with these concepts comes the use of instruments or apparatuses 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 air your basic 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 disposed of the transfer pipette in the indicated waste bends within your lab. So here its primary uses just to transfer small amounts of liquid. Now, here in this next image, this is what is called our Bure ette. Okay, so it's gonna become important that you guys understand how to use of your red You're gonna pour in your liquid into the top of the Bure. It the liquid that you're pouring in is called the Thai Trent. And here let's say that this mark here represents 25 smells. So we've placed in 25 miles of our hydrant, 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 off the Tetris 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 thes two numbers to know how much off 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 your calmly here being used a lot when it comes toe acid based titrate Asians. Okay, so those are the predominant times that we use the Bureau wrecked. 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. 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? 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 this processes could also be called filtration. You're filtering out the solids from the liquid. Now we're gonna say here that this Bucknell 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 out faster so that you re left with these solid particles on the filter paper within the Bucknell funnel. So here this vacuum flask, it aids the Buckner funnel in filtration, 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 year is a graduated cylinder. Typically in your lab, you'll have a small one, which is 10 Els, and you'll probably have a larger one, which could go up to 100 emails. 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 precisely just helping us to figure out, um 10 ml zor 100. Emil's 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 off liquid. We're gonna say the typical size that you'll find in your lab are 250 miles of this, or maybe even 500 miles. Now, next, What we have here is we have a volumetric flask. Now this is used for dilutions. So what we do here is we have our solution here and here. These things are typically 100 miles in size, but there are larger ones that can go upto like one leader. So this is our solution here, and let's Sarah solution is 25 m outs 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 miles in volume. And its concentration is 250.10 Moeller 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, Mark, there is 100 m outs, so I'm gonna fill it up with water, right all the way up to the mark. And when you're doing dilutions with the volumetric flask to make sure you mix it thoroughly, shake it up and down so it makes it 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 Mick 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 mole Arat e volume. This is our initial volume, and then m two represents our final volume our final more clarity or concentration or are 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 10 Moeller off concentration of our solution. Its initial volume was 25 miles. Here. We don't know what it's new concentration will be, but its new final volume is 100 m else. Once we've added all the water we needed, now we do is we divide both sides by 100 you'll be able to find out what your new concentration would be for your solution. So that's the approach we would take in terms off dilution question later on. If you guys haven't done this year, 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 Erlin 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. Okay, 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 rent toe, measure out 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 er, Lemire 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 you're ta 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 chemistry. When we start talking about polarity and moles and grants and terms like that, we'll continue our discussion on other instruments found with the lab later on in 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 off 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. But we're also gonna 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 it's led. Yeah. 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 on 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 in evaporating dish or in 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 play some liquid on this dish and give it time to evaporate, leaving behind a solid. So this here is just used to contain a small amount of liquid s O that it could 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 going to say that this is a scoop Ula. So ah, spatulas when we're trying to take a small amount of countered solid from a container within your lab and maybe place it within a beaker or flask. So this just helps us to transfer small amounts off solid, usually in powdered form and a scuba is just to help us to transfer larger amounts of solid. Because next, what we have here is a basic funnel. Remember, we've seen Ah Buckner funnel earlier, which is used in vacuum filtration here. This is just a regular funnel now its primary uses. So basically it helps us to transfer liquids or solids. If they're in powdered form or or small enough, I'm 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 is possible gets within that flask, another method that we could 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 you're filter paper circular like this, and what you do is first, you fold it in half, and then you'd fold that half and half a swell so you have that, and then you would hold it out like this and just put your hand through it and open it up. It would form basically like a poorest membrane, and you place that within the funnel, and then you can pour a liquid through there. And what what happened 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 yeah, to separate a liquid, which is our fill trait and a solid, which is our residue Now. Finally, what we have here are 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 to transform of liquid or solid in tow. Continue with a smaller opening. This is a separate torrey funnel or separating funnel, and the whole purpose of this secretary funnel. It basically helps us to suck. 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're talking 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 world, 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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Laboratory Materials
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Now that we've gone over some of the basic lab instruments that you're going to 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 m els of a 250.100 Mueller HCL solution and added 2.200 Mueller any 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, his option B, which is the sucks. Let extractor. Now let's not worry about the whole sucks lead 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 to 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 separated into its own separate liquid mixture. So at then you'll have to different liquids separated from one another. But here they're asking us now 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. Pipat Transfer pipette. We have a graduated cylinder, we have a volumetric flask, and we have a direct 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 ml of 250.100 Mueller HCL? Because they say the word exactly. That means we need precision. So precision is needed. A transfer pipe. It would not work because that's just helps us to transfer Ah, small amount of a liquid were not really measuring How much of that liquid we're transferring so wouldn't work. A graduated cylinder is to help us transfer larger amounts of liquid. Here, we only need 25 amount, so it wouldn't be ideal. Ah, volumetric flask. Remember that this is useful when it comes to dilutions, not when it comes to precise transferring of liquids. The best answer here would have to be our bureau. Rhett Bure. It's our great when it comes to the preparation of solutions like I said earlier on, and they're commonly used in acid based iterations. So RB 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 could 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 ah question dealing with a dilution with in the lab
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Laboratory Materials
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What is the polarity of a solution made by mixing 200 miles off pure water with 100 miles off 1000.75 Mueller Potassium chloride solution. All right, so any time we're adding water to any type of solution, that means that we are doing a dilution. Remember, a dilution. Okay, 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 two? The word off means multiply, Which makes sense because this would be my M one. This would be my V one. They're multiplying each other. We don't know what M two is now. The two equals our final volume. Yes, and our final volume equals the volume Initially, that we had plus the volume of added water. So initially we started out with 100 m. Els right here, 100 miles. And what did we do to that 100? Emil's, while we added on additional 200 miles of water so that mean my final volume or V two is 300 NL's. So we have to do now is solved for em, too. So divide both sides by 300 miles. Yes, so we'll just be 0.75 divided by three. So my new polarity would be 0.25 Moeller giving the option B as the correct choice. So remember, in a dilution, your new concentration normal clarity, which is M two, is always smaller than your M one. So this is just a basic dilution question. What? We have to use the dilution formula continuing with this idea of dilutions. Let's 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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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 the classroom. But it's another thing when you're in the lab and asked to do a dilution yourself, the illusions could be a bit tricky. So the approach we wanna take is this. So we want to create 100 fold dilution. Okay, so just remember, in a dilution that means that are 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 where they want us to do 100 fold dilution, so that means it's gonna be a ratio of 100 to 1. Well, 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 it's ratio to the amount of solution. Okay, so that's what the 100 toe one is referring to 100 fold. Dilution is 100 to 1. Maybe we have ah 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 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 to dilution or a tenfold dilution, which is not what we want next for See, 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 to 1. This would represent our 100 fold dilution If we take a look at the last ones here we have 100 plus one toe, one that be 101 toe one. Not quite what we want. This would be 101 full dilution which is not what we want. And then the last one would be 10 plus one toe one, 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.