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. What's important here is to be able to identify the apparatus and what its primary use is.

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 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 the 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 are holes within this Buchner 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.

Okay? The liquid portion will go through the holes and down here and what's left behind is our solid particles. Alright. 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. Sometimes we'll use the Buchner funnel with this volume, volume flask.

We place the Buchner funnel here and we attach the tube to the tubing right there. We turn on the vacuum suction. It would help the water to come down faster, and it basically aids in 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 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 of 0.20 molar of some type of solution. Right? So we place that in here and then 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 a 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 a 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, 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, we 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 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 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 use is 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 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 will be left behind would be some solid. That solid is sometimes referred to 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 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 is a separatory funnel 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 TA says within the lab. Always be careful when transferring any liquids or solutions. Follow all the rules. Study, 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 talked about basically all of these different instruments. But the one that we haven't talked about is option b, which is the Soxhlet extractor. Now let's not worry about the whole Soxhlet 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 Soxhlet 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 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 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 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 a burette. Burettes are great when it comes to the preparation of solutions, like I said earlier on, and they're commonly used in acid-based titrations. So, our 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 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 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 molar potassium chloride solution? Alright. So, anytime we are adding water to any type of solution, that means that we are performing a dilution. Remember, a dilution occurs anytime we're adding, mixing, or titrating with water. And when it comes to dilution, we use the dilution formula which is MV1=MV2.

So, they're asking us, what is the molarity after we've added this water, which translates to asking for MV2. The word "of" means multiply, which makes sense because this would be my MV1, they're multiplying each other. We don't yet know what MV2 is.

Now, Vt2 equals our final volume, and our final volume equals the initial volume we had plus the volume of added water. Initially, we started out with 100 ml here, 100 ml. And what did we do to that 100 ml? Well, we added an additional 200 ml of water.

So that means my final volume or Vt2 is 300 ml. All we have to do now is solve for MV2. So divide both sides by 300 ml. It would just be 0.75 divided by 3. So my new molarity would be 0.25 M, giving me option B as the correct choice.

So remember, in a dilution, your new concentration or molarity, which is MV2, is always smaller than your MV1. This is just a basic dilution question when 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. Once again, if you get stuck and don't know where to go, come back and take a look at the next example video where I explain 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 is another thing when you are 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. So we want to create a 100 fold dilution, okay?

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 100 to 1. But what exactly is the 100 referring to, and what exactly is the 1 referring to? In terms of a dilution, we're going to 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. A 100 fold dilution is a 100 to 1, meaning we have 100 when it comes to adding up the amount of solvent and solution together, compared to 1 for the solution. So here we know that option 'a' is out. If we look at the other options, what do we have? For option 'b', we have 90 parts solvent and 10 parts solution, so that would be 90+10, which totals 100, compared to 10 for the solution alone. 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+1, and then 1 for the solution, making it 100, which represents our 100 fold dilution.

If we look at the last options, here we have 100 parts solvent plus 1 part solution, so that would 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 option would be 10 parts solvent plus 1 part solution, so that'd be 11 to 1. This would be an 11 fold dilution. So 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. A 100 fold dilution 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.