Volumetric Instruments - Online Tutor, Practice Problems & Exam Prep

In a chemistry laboratory, various instruments are essential for experiments. A transfer pipette is used for transferring small liquid amounts, while a burette measures liquid volumes for titrations. Graduated cylinders and beakers serve to measure and hold larger liquid quantities. For solids, crucibles heat materials at high temperatures, and evaporating dishes facilitate evaporation to leave solids behind. Funnels assist in transferring liquids and solids, with filter paper used for separation. Understanding these tools enhances practical application of concepts like acid-base reactions and solution preparation.

Laboratory Materials 1

Hey everyone. So in this video, we're going to take a look at some instruments that you're going to eventually see within your typical chemistry laboratory. Now remember, the laboratory is just a way of us taking what we're learning within the lecture and applying it in real life through experimentation. Now let's take a look at some of these apparatuses. And what's important here is to be able to identify the apparatus and what is its primary use. Alright. So for the first one, we have what's called a transfer pipette. These transfer pipettes are usually made up of basic or cheap types of plastic, and the whole point of it is, within a name, to transfer small amounts of liquid.

For the next one to the right of it we have what is called a burette. Now in this burette, you pour in your liquid in here, sometimes this liquid is called a titrant. And let's say that it measures here to 25 ml, and let's say I open up this stopcock here, and I let the water go down so it's dripping out, and let's say it goes and we stop it at 18 ml's. We would say 25 minus 18, we'd say that 7 ml's have been delivered through the use of this burette. So what's the whole point in use of a burette? Well, one predominant use of it is to help prepare solutions. And a second use for it, what you're going to eventually do if you haven't already, is for acid-based titrations.

Next, we have a funnel. Here this one is in particular called a Buchner funnel. And typically there's holes within this button or funnel here and what we do is we place a filter paper on top of it. So basically its predominant use is for filtration where we separate solids from liquids. The liquid portion will go through the holes and down here, and what's left behind is our solid particles.

Next here, we have is a vacuum flask. It's a vacuum flask because it has this little attachment here, which you can connect the hose to. And sometimes we'll use the Buchner funnel with this vacuum flask. We place the Buchner funnel here and we attach basically the tube, the tubing right there. We turn on the vacuum suction. It would help the water to come down faster, and it basically aids the filtration of the Buchner funnel.

Next, what we have here is just a typical graduated cylinder. So what's the whole point of a graduated cylinder? It's just to measure volume. So measure out volumes. The thing with this one is it's not as precise so you're just trying to transfer a certain amount. You don't care too much about precision, you're just trying to move a good amount of liquid.

Here, this next one is a beaker. These beakers can come, pretty large. They can go from 250 ml or 500 ml as the typical sizes. Now there are sizes that range outside of these, outside of this range, but typically you'll see 250 to 500 within your laboratory. And here this is just to measure out larger quantities of water, or larger quantities of a liquid.

Next, we have what's called a volumetric flask. Now, what's the whole point of a volumetric flask? We use them for dilutions. So let's say that we have, 10 ml's of 0.20 molar of some type of solution. Right? So we place that in here, and then what we do is we fill up the rest with water up to this line. And then we would invert it and mix it thoroughly in order to dilute that previous solution. So here a volumetric flask just helps us to dilute our initial solution or concentrated solution. These can range in different sizes, some can even go up as high as 1 liter. You may not see that within your laboratory, but realize that it's possible.

And then finally here, what we have is an Erlenmeyer Flask. What is its predominant use? It's just to help us transfer large amounts of solutions. So some of these are typical types of instruments you'll come into contact with within your chemistry laboratory. So just familiarize yourself with the image, the name, and their predominant use.

Laboratory Materials 2

In this video, we continue our discussion of laboratory instruments and their use within our basic chemistry laboratory. So here we are going to say, we are going to continue with our discussion. We are still going to look at solutions and the transferring of them. But we are 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 what's called a crucible, which is the container, and its lid. Now within your basic chemistry laboratory, 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 our crucible we're going to say is used to heat small amounts of solid material at high temperatures. Now we're going to say here that when our substance is wet, we're going to 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, we have here an evaporating dish or an evaporation dish. In this case, we don't use an oven in order to heat 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 to contain a small amount of liquid 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 are spatulas. And here we're going to say that this is a scoopula. So a spatula is when we're trying to take a small amount of powdered solid 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 a scoopula is just to help us to transfer larger amounts of solid.

Next, what we have here is a basic funnel. Now remember, we've seen a Buchner funnel earlier, which is used in vacuum filtration. Here, this is just a regular funnel. Now its primary uses to basically, it helps us to transfer liquids or solids if they're in powdered form 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 pour it 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 the lab, they'll teach you how to fold a filter 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 in 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'd 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 would be left behind would be some solid. That solid, sometimes we refer to it as a residue. So if filter paper is used, it can be used to separate a liquid, which is our filtrate, 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 Buchner 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 separatory funnel or separating funnel. And the whole purpose of this separatory funnel, it basically helps us to support its this 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 dealing with acid-base extractions. So we'll talk in greater detail about what exactly is an acid-base extraction and how exactly a separatory funnel is used 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 setting. So just follow what your professor says or your teaching assistant says within the lab. Always be careful when transferring any liquids or solutions. Follow all the rules. Study, and you should be able to do well within your lab.

Laboratory Materials

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 to measure out exactly 25 ml of a 0.100 molar HCl solution and add it to a 0.200 molar NaOH solution, which instrument would be most useful? At this point, we've discussed basically all of these different instruments. But the one that we haven't talked about is option b, which is the suck sled extractor. Now let's not worry about the whole, suck sled extractor portion. That's just a specific type of extractor. Let's focus on what 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 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 suck sled extractor. We'll talk more about distillation later on.

Next, we have a transfer pipette, a graduated cylinder, a volumetric flask, and a burette. Now all of these deal with measuring out a quantity of a liquid. But in the question, they're saying which one will measure out exactly 25 ml of 0.100 molar HCl. Because they use the word exactly, that means we need precision. A transfer pipette would not work because that just helps us to transfer a small amount of a 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 dilutions, not when it comes to precise transferring of liquids. The best answer here would have to be our burette. Burettes are great when it comes to the preparation of solutions, like I said earlier, and they're commonly used in acid-based titrations. So a burette here would be the best choice. If you don't quite remember what each of these instruments looks 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. 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 we approach a question dealing with a dilution within the lab.

Laboratory Materials

What is the molarity of a solution made by mixing 200 ml of pure water with 100 ml of 0.75 M potassium chloride solution? Alright, so anytime we are adding water to any type of solution, that means we are doing a dilution. Remember, a dilution is anytime we're adding, mixing, or titrating with water. And when it comes to dilution, we use the dilution formula which is m₁v₁=m₂v₂. They are asking us what the molarity is after we have added this water. So, we need to find what m₂ is. The word 'of' means multiply, which makes sense because this would be my m₁ and this would be my v₁; they are multiplying each other. We don't know what m₂ is. Now v₂ 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 ml here, 100 ml. What did we do to that 100 ml? We added an additional 200 ml of water. That means my final volume or v₂ is 300 ml. To solve for m₂, divide both sides by 300 ml. It would just be 0.75 divided by 3. So, my new molarity would be 0.25 Molar. This makes option B the correct choice. Remember, in a dilution, your new concentration or molarity, which is m₂, is always smaller than your m₁. This is just a basic dilution question where we have to use the dilution formula.

Continuing with this idea of dilutions, let's see if you guys can figure out how to answer example 3. 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.

Laboratory Materials

So for our final example question on this page, we are going to deal with a dilution. Now, it is 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. Dilutions can be a bit tricky, so the approach we want to take is this: we want to create a 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. Knowing this, we know that option a won't work because in option a, the solvent is less than our solution. So that's not going to work. And when it comes to a dilution here, they want us to do a 100-fold dilution. So that means it's going to be a ratio of a 100 to 1. But what exactly is the 100 referring to and what exactly is the 1 referring to? When it comes to a dilution, we're going to say here it is the solvent plus and its ratio to the amount of solution. Okay. So that's what the 100 to 1 is referring to. A 100-fold dilution is a 100 to 1, meaning we have a 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 option a is out. So if we take a look at the other options, what do we have? For option b, we have 90 solvent plus 10 solution. So this would be 90 plus 10, and then this would be 10. So that would total up to 100 to 10, and this would represent, if you divide both by 10, this would represent a 10 to 1 dilution or a 10-fold dilution, which is not what we want. Next, for option c, we have 99 parts solvent plus 1 part solution. So that'd be 99 plus 1, and then 1, so that would be 100 to 1. This will represent our 100-fold dilution. If we take a look at the last options, here we have 100 plus 1 to 1. So that'd be 101 to 1. Not quite what we want. This would be a 101-fold dilution, which is not what we want. And then the last one would be 10 plus 1. So that'd be 11 to 1. So this would be an 11-fold dilution. So here, just remember, in 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 just the amount of the solution.

Here’s what students ask on this topic:

What is the primary use of a burette in a chemistry laboratory?

A burette is primarily used for titrations in a chemistry laboratory. It allows for the precise measurement and delivery of liquid reagents, known as titrants, to a solution. By controlling the amount of titrant added, chemists can determine the concentration of an unknown solution through acid-base reactions or other titration methods. The burette's stopcock enables accurate control over the liquid flow, making it essential for experiments requiring high precision.

How does a volumetric flask differ from a graduated cylinder?

A volumetric flask is designed for precise dilutions and preparation of standard solutions. It has a single calibration mark indicating a specific volume, ensuring high accuracy. In contrast, a graduated cylinder has multiple graduation marks along its length, allowing for the measurement of various volumes but with less precision. Volumetric flasks are ideal for making solutions of exact concentrations, while graduated cylinders are used for general volume measurements where high precision is not critical.

What is the function of a crucible in a chemistry lab?

A crucible is used to heat small amounts of solid materials to high temperatures in a chemistry lab. It is typically made of materials that can withstand extreme heat, such as porcelain or metal. Crucibles are essential for processes like calcination, where a substance is heated to remove volatile components, or for melting and fusing materials. They are often used in conjunction with a lid to contain the material and minimize contamination.

When would you use a Buckner funnel instead of a regular funnel?

A Buckner funnel is used for vacuum filtration, which is a faster and more efficient method of separating solids from liquids compared to gravity filtration with a regular funnel. The Buckner funnel, combined with a vacuum flask and a vacuum source, creates a pressure differential that speeds up the filtration process. This setup is particularly useful when dealing with fine particles or when a quick separation is required.

What is the purpose of a separatory funnel in a chemistry lab?

A separatory funnel is used to separate immiscible liquids based on their densities. It is commonly employed in liquid-liquid extractions, such as acid-base extractions, where one liquid phase is used to extract a compound from another. The funnel allows for the controlled release of the lower density liquid through a stopcock, facilitating the separation of the two phases. This tool is essential for purifying compounds and isolating specific components from mixtures.