Hello, my name's Mrs. Niven, and today we're going to be talking about concentration of solutions using moles as part of our unit on making salts.

Now, you may have some experience of what we do in today's lesson from your previous learning, but what we do today will help us to not only answer those big questions of what are substances made of, how can they be made, and then how can they be changed, but we'll also be able to better appreciate the simple solutions that we come across in everyday life.

So by the end of today's lesson, you should hopefully feel more confident being able to explain what we mean when we talk about the concentration of a solution, as well as be able to calculate it for various solutions.

Now the key words that we'll be using throughout the lesson as well as their definitions are provided on the next slide.

You may wish to pause the video here so you can jot them down for reference later on in the lesson or later on in your learning.

Today's lesson is broken into three parts.

We'll start by looking more closely at describing what we mean when we talk about concentration before looking at the units for concentration, and finally calculating concentration.

So let's get started by looking at what we mean when we use that term concentration.

Many chemicals that chemists come across and use are found in their aqueous form and these are indicated to us using that state symbol of aq, which you may recall, simply means that a substance has been dissolved in water and exists as a solution.

So we have an example here of sodium chloride that has dissolved in water.

Then we have copper sulphate and many of the other chemicals that we commonly use in the science lab are also found in that aqueous form as a solution.

Things like acids.

Here we have sulfuric acid and our alkali here, sodium hydroxide, and we can tell that all of these are a solution simply by looking at their labels because they have that aq state symbol.

Now a solution is composed of a solute that's dissolved in a solvent.

Now the solvent in an aqueous solution is simply water, H2O.

So the solute is our solid here, the solvent is our liquid that it's dissolving into, and the resultant mixture then is a solution.

Let's stop here for a quick check.

"Which of the following statements is true about an aqueous solution of sugar?" Well done if you said A and D.

Because it's an aqueous solution, we know that water is the solvent and we'd be able to show that it's a solution using that state symbol of aq.

So very well done if you've got at least one of those correct and extremely good start to this lesson, if you managed to choose both of those correct answers.

Fab work guys, keep it up.

Now the thing about using the term concentration is that it actually has been used to explain a few different things in everyday life.

For instance, you might describe somebody focusing on their work as concentrating, or having good concentration on that work.

The word concentration has even been used to describe World War II camps, and it might even be used to describe drinks as a concentrated drink.

But in chemistry specifically, concentration is used to describe a solution in terms of its solute and its solvent.

Concentration is simply a ratio of solute particles to the volume of solvent that those particles are dissolved in.

Now you may recall that volume represents the amount of space that a substance occupies.

So if we wanted to find the volume of this cube, we'd simply multiply its length times its width times its height, and we could say that the volume of this particular space is 1,000 centimetres cubed or one decimeter cubed.

So if I had two solutions of the same volume, concentration can help to indicate how crowded those solute particles are when they're dissolved in that solvent.

For instance, if I had one decimeter cube of solvent and I only had a few particles of solute dissolved in it, I could describe the concentration of that solution as being low.

Few particles of solute, quite a low concentration.

If I had more particles dissolved in the same volume of solvent, so many particles, I would describe that concentration as being high or higher than the other one.

So many particles dissolved in a solvent gives us a high concentration, and we can see that without having to zoom in to those solutions because higher concentration solutions tend to appear quite dark.

Now I can control or adjust the concentration of a solution by changing the amount of solute that is dissolved in a specific volume of solvent.

So if I add a large amount of solute into a specific volume of my solvent, I'm putting many solute particles dissolving in that volume, and I get a higher concentration.

If I want a lower concentration, I'm going to add a smaller amount of solute providing fewer solute particles, and that would then result in that lower concentration.

Another way that I might be able to adjust the concentration of a solution is by adding distilled water to that aqueous solution because what that does is it increases the volume of the solvent, so increases the space in which those solute particles are dissolved in.

Now what that actually is doing is diluting that original solution.

So a diluted solution has a lower concentration than the original solution.

So if my original solution has a high concentration of solute particles dissolved in a specific volume of solvent and I add some water to it, I end up with a larger total volume of solution.

But those solute particles are now spread out within that larger volume, creating a lower concentration.

Now it's really important if you're diluting a solution that you use distilled water because what that does is ensure that there are no other substances present in that solution.

You still have the same solvent with the same solute particles.

Let's take a moment for another quick check.

True or false.

"Solution X has a lower concentration than solution Y," and I'd like you to explain your answer.

So justify your choice on whether or not that statement is true or false.

Well done if you chose false.

Now, there were a few different ways that you could justify that answer.

You could have said that "Solution X is darker in colour suggesting that it contains more solute particles," and therefore a higher concentration.

Or you could have referred to solution Y saying, "That that is lighter in colour, suggesting that it contains fewer solute particles," and therefore a lower concentration.

So very well done if you managed to choose the correct answer of it being a false statement, but incredibly well done if you were able to justify your choice with your explanation.

Great job guys.

Well done.

Okay, time for the first task in today's lesson.

What I'd like you to do is use words from the box to complete the passages below.

So pause the video and come back when you're ready to check your answers.

Okay, let's see how you got on.

Now, if you completed the passages correctly, it should read out like this.

"If a substance dissolves in water, it is said to be soluble.

The substance that dissolves is known as the solute and the water is the solvent.

The resulting mixture is known as a solution.

Chemists often carry out reactions in solution.

As such, the concentration of each solution used should be stated.

This informs others about how much substance has dissolved in a certain volume of solvent." Well done if you managed to get that correct.

If you use the incorrect word at any point, please do make sure that you've corrected that as we went through this so that you have a complete summary of what we mean by concentration.

Well done though if you managed to get those correct, guys.

Great job.

For this next part, I'd like you to use your understanding of concentration to help Jacob.

He's been asked to create a sweet cordial drink for his grandmother, but she thinks it tastes a little too sweet.

So what could Jacob do to change the concentration of his grandmother's drink so that it tastes less sweet? And I'd like you to explain how your suggestion would help him.

So pause the video here, and come back when you're ready to check your answers.

Okay, let's see how you got on.

Now, the best way to do this would be to simply add some water to his grandmother's drink because that would dilute the drink, making it less concentrated and that would help to make that drink taste less sweet.

We really don't want to be creating a whole new drink by pouring out what he's already made and then simply putting in less of that cordial to create that drink, which you could have done because that's just wasteful.

So if you did say start over, use less of the cordial drink and add some more water, then that would still be a correct answer, but the better answer would be to use the drink you started with and simply add some water to it.

Well done though if you managed to suggest to add water and very well done if you were able to explain how that would fix his grandmother's drink.

Very well done guys.

Great start to this lesson.

Now that we're feeling more comfortable being able to describe what we mean when we talk about concentration, let's look more closely at the units that are used to describe it.

When we're provided with the value for the concentration of a solution, hat that value is actually representing is a ratio between the solution's number of solute particles to the volume of solvent that's been used.

Now, the volume of a solution or the amount of space that that solution occupies is equal to the volume of the solution's solvent and that tends to be measured out using a measuring cylinder.

Now, different situations may call for different volumes.

For instance, if you're going to be using a solution for an investigation in the laboratory versus using a solution for an industrial process.

Now because of that, it's important to understand that volume can be quoted in a variety of units.

So I have an example here.

A thousand millilitres is equal to 1,000 centimetres cubed.

Now that's the same volume as one decimeter cubed or one litre.

Now these smaller volume units of millilitres and centimetres cubed tend to be used for investigations in the laboratory, whereas those larger units of decimeter cubed and litres may be used for an industrial process.

Now, if you're doing an investigation in the laboratory using those units of centimetres cubed but want to upscale it for an industrial process, you would then need to be able to convert between your investigation unit of centimetres cubed to your industrial unit of decimate cubed, and to do that, you would simply divide your value by a thousand.

Similarly, if you had an idea for an industrial process but wanted to investigate it in the laboratory first, you might take that decimeter cubed value and have to multiply by a thousand to convert it to centimetres cubed to use in the an investigation in the laboratory.

Now, a measuring cylinder measures volume in centimetres cubed, but the standard unit for concentration quotes volume in decimeter cubed.

So we'd need to be able to convert between our centimetres cube and decimeter cube when doing any of those calculations in the laboratory.

Now you could do that easily by dividing by a thousand or we can use a simple rhyme to help us do the same thing, "c to the d; 1, 2, 3." Let's look at an example.

I have 500.

0 centimetres cubed.

I changed my c to a d simply by adding that line, and then I'm going to move the decimal point three places to the left, 1, 2, 3.

Following that rhyme then, 500 centimetres cubed is equal to 0.

500 decimeter cube simply by changing the c to a d, and then moving that decimal place three places to the left.

Let's stop here for a quick check.

"What is the volume in decimeter cubed of 15.

2 centimetres cubed?" Well done if you said C.

Now you could have done it in two ways.

You could have either divided that volume by a thousand or you could have used our rhyme c to the d; 1, 2, 3, and you'd have got the same answer of 0.

0152 decimeters cubed.

So well done on getting that first one right, guys.

Fab work.

The number of solute particles that have dissolved in that volume of solvent then is measured in moles.

Now, you may recall that one mole is equal to 6.

02 times 10 to the 23 particles.

Now, we can't measure out a mole of solute particles because one, it's too difficult.

We can't actually individually pick up one particle at a time, and secondly, it would take far too long to count that number of particles.

So instead we use that mathematical relationship of mass in grammes is equal to the relative mass of the substance times the number of moles that are being used, and we use that then to calculate the mass that we can then measure out on a balance of the solute that we would like to dissolve in our solvent.

So let's take a moment to remind ourselves how to use that mathematical relationship.

If I want to know what the mass is of 0.

015 moles of zinc carbonate to two significant figures, the first thing that I need to do then is to actually calculate the relative mass of the substance, which is zinc carbonate.

And to do that, all I'm going to do is add up the mass for each atom in that substance and I get a value of 125.

4.

I then take that value and multiply it by the number of moles which was given to me in my question, and that gives me an answer of 1.

881, but to two significant figures then, the final mass should be 1.

9 grammes.

What I'd like you to do now then is to please calculate the mass of 0.

0075 moles of potassium permanganate to two significant figures.

So make sure that you're showing all your working out.

Perhaps check your answers with the people nearest you, pause the video and come back when you're ready to check your answer.

Okay, let's see how you got on.

If you've done your calculations correctly to two significant figures, you should have a final answer of 1.

2 grammes.

If you didn't get that answer, please do pause the video to check your workings out against what is shown so we can identify any errors and see how we can avoid them going forward.

But very, very well done if you manage to get that correct, guys.

Great job.

So once you know the mass of solute required for a particular concentration, you can measure that out then using a balance.

Now, a solute's mass can be measured in different units, just like the volume could be measured in different units or quoted in different units.

But for concentration, the standard unit for the mass of solute is in grammes, but like volume, you can convert between different units, milligrammes for instance or kilogrammes and between them all the way along.

And what you'll notice as you move from the smaller unit on the left of milligrammes, up to the larger units of kilogrammes on the right, we are dividing by a thousand and as we move from kilogrammes, that large unit down to milligrammes, we're going to be multiplying by a thousand, which means then 1,000 milligrammes is equal to one gramme, which is also equal to 0.

001 kilogrammes.

Now because a solution is made up of particles of solute that's been dissolved in a volume of solvent, the concentration of that solution needs to be quoted in terms of the units for both of those components.

So standard units for concentration could be quoted in either grammes per decimeter cubed or moles per decimeter cubed.

Now these can also be written as g dm -3 or moles dm -3.

Let's stop here for another quick check.

"Which of the following could be units for concentration?" Well done if you chose A, C, and D.

Now, C is the standard unit for concentration, but A and D both show a ratio of the number of particles per a unit of volume and therefore, could also be considered a unit for concentration.

So very well done if you at least got C, and spectacular work if you also managed to choose A and or D as well.

Great job, guys.

Let's move on to the second task in today's lesson.

hat I'd like you to do here is to please place each word or phrase into the appropriate column based on how you might group these ideas as either being related to a solute, related to the solvent, or related to the solution.

So pause the video and come back when you're ready to check your answers.

Okay, let's see how you got on.

For the solute, I would've put quite a few of those options in there.

So we're talking about the number of particles, grammes, mass, milligrammes, kilogrammes, balance, and moles.

So we're looking at the units, what those units represent, and how it would measure out some of that solute itself.

For the solvent then, I would've put centimetres cubed, water, decimeters cubed, and measuring cylinder.

And for solution then, moles per centimetre cubed, mixture, and grammes per decimeter cubed.

Very well done if you managed to get those correctly matched up, guys.

Great job.

For the last few questions in this task then, I'd like you to do a few conversion calculations and to give your answers to two significant figures.

So as always, please do show you're working out so that we can identify any errors if they do crop up when we go through the answers later, and pause the video and come back when you're ready to check your answers.

Let's see how you got on then.

2A, you should have an answer of 0.

046 decimeters cubed, and B then should be 250 centimetres cubed.

3A then should be 3,500 grammes, and b then should be 0.

0068 grammes.

For this last question then, you needed to use that mathematical relationship of the mass is equal to the relative mass times moles.

For letter A then, you should have had a final answer of 76 grammes, whereas for B, then you would've had a final answer of 170 grammes.

Remembering that these final answers should be to two significant figures.

So very well done if you manage to get this correct.

Great job, guys.

Now that we know a little bit more about what we mean when we talk about concentration and the units that are involved when describing it, let's move on to look at how we can calculate the concentration of various solutions.

We need to remember that concentration is simply a ratio of the number of particles of solute that have dissolved in a particular volume of solvent.

What that means then is that equal volumes of solutions that have the same concentration will have the same number then of dissolved solute particles and to double check that, we could calculate the concentration of that solution using two different equations.

The concentration is equal to moles divided by volume or concentration is equal to the mass of our solute divided by the volume it's dissolved in.

And we can actually convert between these two equations or mathematical relationships using that other mathematical relationship that the mass in grammes of our solute is equal to the relative mass of each individual particle times moles, or the number of particles that have actually dissolved.

Let's stop here for a quick check.

"Which two of these samples have the same number of dissolved solute particles?" You may wish to pause the video so you can discuss your ideas with those around you, and then come back when you're ready to check your answers.

Well done if you chose A and D.

Both of these solution samples have the same number of dissolved solute particles because they have the same concentration and the same volumes when you convert those units and make them equivalent.

So very, very well done if you chose that pairing, guys.

Great job.

Let's look at how I can use that mathematical relationship using concentration.

I'd like to know what the concentration is in grammes per decimeter cubed of a solution that is composed of 15 grammes of sodium chloride that has dissolved and 0.

35 decimeters cubed of water, and I want to know that concentration to two significant figures.

So I know I'm going to need to use this relationship of concentration is equal to mass divided by volume, and I know that one because I've been given the units in grammes per decimeter cube.

And also when I look at the other values for my solute in solvent, I can see that I've been given those values in grammes and decimeters cubed.

Now because of that, all I need to do is pop those values into the correct position within my mathematical relationship, so 15 divided by not 0.

35 gives me a concentration of 42.

86, but to two significant figures then, my final answer should be 43 grammes per decimeter cubed.

What I'd like you to do now then is to please calculate the concentration in grammes per decimeter cubed of a solution that's composed of 5.

2 grammes of sugar, dissolved in 1.

6 decimeter cubed of water, and again, to give your answer to two significant figures.

So please pause the video here while you'll do your working out, and then come back when you're ready to check your answer.

Okay, let's see how you got on.

If you've carried out your calculations correctly then to two significant figures, you should have a final answer of 3.

3 grammes per decimeter cubed.

If you didn't manage to get that, please do pause the video here so you can check through your working out, and identify any errors that we could try to avoid going forward, but very well done if you managed to get that correct.

Great job guys.

Let's look at another example.

This time I want to know the concentration in moles per decimeters cubed of a solution that contains 0.

50 grammes copper sulphate dissolved in 0.

25 decimeters cubed of water, and I want that answer to two significant figures.

So I'm going to be using the relationship concentration is equal to moles divided by volume because I've been asked to quote the concentration in moles per decimeters cubed.

Now the values that I have to work with are 0.

50 grammes of copper sulphate, and 0.

25 decimeters cubed of water.

Now when I look at that, I'm going to need to convert the grammes of my solute into moles.

So the first thing I do is find the relative mass for a particle of copper sulphate by adding up the masses of each atom in that particle and I get a number of 159.

6.

To find the number of moles then, I'm going to take the mass of 0.

50 grammes, and divide it by the relative mass of 159.

6, and that tells me the number of moles.

So I now have the number of moles that have dissolved, and the volume of solvent that it dissolved into, and that gives me a concentration.

However, I need to quote this to two significant figures.

So my final answer will be 0.

013 moles per decimeters cubed for my concentration of my copper sulphate solution.

What I'd like you to do now then is to calculate the concentration in moles per decimeter cubed of a solution that contains 0.

25 grammes silver nitrate dissolved in 0.

15 decimeter cubed of water, and to give your answer to two significant figures.

So pause the video, show you working out, maybe discuss your ideas with the people around you and then come back when you're ready to check your answers.

Okay, if you've done your calculations correctly, you should have a final answer to two significant figures of 0.

0098 moles per decimeters cubed.

The key here is to make sure that you have calculated the moles correctly for your silver nitrate, so I would recommend checking your relative mass as a starting point if you didn't get that correct answer, but very, very well done if you managed to get that correct, guys.

Excellent work.

Now, like all mathematical relationships, our equation for concentration can be rearranged in order to calculate an unknown volume of solvent or the mass of solute to be used.

So we could take this equation of concentration equals mass divided by volume, and rearrange it so that the volume of solvent we may need is equal to the mass that's being dissolved, divided by the concentration, and that the mass of the solute that's used would be equal to the concentration times the volume.

Now, the thing to remember here is that the values for our solute and or our solvent may need to be converted into those appropriate units before we calculate the solution's concentration.

So remember that the solvent, so the volume then, needs to be in cubic decimeter or dm cubed, and the solute then must be in moles or grammes, and you'll decide which one that is based on the concentration units.

When you're being asked to calculate an unknown value, it's usually helpful to employ a strategy.

So my suggestion would always be to make sure the first thing you do is choose the appropriate equation for what you're being asked to calculate.

Is it concentration, the particles, so that's the moles of the mass, or the volume of the solvent when we're talking about concentration, The next thing you need to do is identify the values you have available in your question, and ensure that they're all in the correct units that you need for your equation that you're using and that may need some converting.

So remember, the number of particles of your solute will be in moles or grammes.

The volume should be in decimeters cubed, and then the concentration then will be either in moles per decimeters cubed or grammes per decimeters cubed.

And then finally, once you have those values in the correct units for the equation you need to use, you can simply put those values in that equation and solve for your unknown.

Let's have a go at using that strategy then.

I want to know what massive solute must dissolve in 250 centimetres cube of water to produce a solution that has a concentration of 2.

3 grammes per decimeters cubed.

And I want my answer to two significant figures.

The first thing I notice is I've been asked to calculate a mass of solute.

That means I need to use that mathematical relationship of mass is equal to concentration times volume.

The next thing I'm going to do is to go back and circle any of the values and their units within the question.

And the reason I do that is I can then easily compare the units to see if anything needs converting.

And I notice here that the volume's been provided in centimetres cubed, but I need it in decimeter cubed.

So by converting that, by dividing by a thousand or using my rhyme c to the d; 1, 2, 3, I have a new volume of 0.

250 decimeters cubed.

I now have a concentration and a volume that I can stick into my relationship.

So 2.

3 times 0.

250 gives me a mass of 0.

575, but to two significant figures, that final answer then is 0.

58 grammes.

What I'd like you to do now then is to calculate what volume was used to dissolve 0.

0102 moles of potassium sulphate that creates a solution with a concentration of 1.

10 grammes per decimeters cubed, and please give your answer to two significant figures.

So you'll need to pause the video, show you're working out, check your answers as you go along with the people around you, and then come back when you're ready to check your work.

Okay, let's see how you got on.

Now, if you've done your calculations correctly, you should have a final answer of 1.

6 decimeters cube to two significant figures.

And as before, what we needed to do was to calculate that relative mass, and that's an area where people tend to go wrong first.

So just double check that you have done your calculations correctly, checking your work and comparing them here.

So if you have made any errors, you can try to correct them going forward, but excellent, excellent work, guys.

I'm so impressed with your perseverance here.

Keep it up.

Time to move on to the last task in today's lesson.

What I'd like you to do is to help Andeep.

He's preparing to make some solutions of sodium sulphate.

So what I'd like you to do is calculate what massive solute he needs to dissolve in order to produce these solutions, and please give your answers to two significant figures.

So pause the video here, and come back when you're ready to check your answers.

Let's see how you got on.

So for part A, you needed to use that relationship of mass as equal to concentration times volume, and we compare the units that we've been provided of the values.

We notice that the volume needs to be converted to decimeter cubed.

Once that has happened and you put the values into your relationship, you get a final answer to two significant figures of 13 grammes.

For part B then, we needed to use the relationship of moles as equal to concentration times volume because the concentration was quoted in moles.

Now, when we do that, we find that there were 0.

015 moles of sodium sulphate that had dissolved.

If we then find the relative mass for the sodium sulphate of 142.

1, we can then use that to calculate the mass in grammes that would've dissolved and to two significant figures, that is 2.

1 grammes.

So very well done if you managed to get that correct.

Great job, guys.

For this next question, let's start applying our understanding of concentration to more familiar solutions.

A mug of instant coffee contains 70 milligrammes of caffeine dissolved in 50 centimetres cubed of hot water.

hat is the concentration of caffeine in milligrammes per centimetres cubed and moles per decimeters cubed? And please give your answers to two significant figures.

So pause the video here and come back when you're ready to check your work.

Let's see how you got on.

We've been asked to find the concentration, so we're going to be using that relationship of concentration is equal to mass divided by volume.

Now we've been asked to find the concentration in milligrammes per centimetres cubed, which is exactly the units we've been given for our solute and our solvent.

So simply dividing those values gives us our answer to 1.

4 milligrammes per centimetres cubed to two significant figures.

Part B was a little trickier to complete, but let's see how you got on.

For this calculation, I'm going to need the mathematical relationship of concentration is equal to moles divided by volume, and when I look more closely at the values that have been provided, I don't have moles, so I'm probably going to need to use that relationship of moles as equal to the mass divided by the relative mass.

Also, when I look more closely at the units, both of them need converting to the standard unit.

So volume will be divided by a thousand to change from centimetres cube to decimeter cubed and mass will also be divided by a thousand to change from milligrammes into grammes.

At this point then, I need to find the relative mass for a molecule of caffeine.

By adding up the relative masses for each of the atoms in that molecule, I get a relative mass of 194.

0.

Using that and my mass in grammes, I can now calculate the number of moles that are present in this solution.

So now that I have the number of moles and I have the volume in decimeter cubed, I put those two values into my mathematical relationship and to two significant figures then, my final answer is 0.

0072 moles per decimeter cubed.

Incredibly well done.

If you manage to get that answer, please, please, please do be kind to yourself and make sure that you're giving yourself marks for these unit conversions.

And for the extra calculations, we need to do to convert between the mass sample and the number of moles that are present.

Each of these would be worth a mark on an exam.

So even if you didn't get that final answer, please do make sure that you're giving yourself credit for the other calculations you've done.

It's not an easy task, and persevering is key.

So incredibly well done guys.

Great job.

Another common solution you might find relates to children's medicines.

Now, some children's medicine contains paracetamol, which is a painkiller, and the concentration of paracetamol in those medicines is 24 grammes per decimeter cubed, and a single dose of that medicine should contain 120 milligrammes of paracetamol.

So the first thing I'd like you to do is to calculate what volume of medicine in centimetres cubed will contain the required mass of paracetamol for a single dose.

And for the next thing I'd like you to do then is to calculate how many moles then of paracetamol are in a single dose, and to give that answer to three significant figures.

Pause the video here, show your working out, compare your ideas, strategies, and answers with the people around you, and come back when you're ready to check your work.

Okay, let's see how we got on.

So I know that I need to calculate the volume of medicine.

So I'm using the relationship volume is equal to mass divided by concentration.

And when I take a closer look at the values that have been provided, I notice that the mass has been given to me in milligrammes, so I need to convert that to grammes as the standard unit by dividing by a thousand.

I then use the new values and my concentration value into my relationship, and I get an answer of 0.

005 decimeters cubed.

However, I've been instructed to give that final answer is centimetres cubed.

So I need to convert my volume in decimeter cubed to the correct units, and I do that by multiplying by a thousand.

That gives us a final answer of five centimetres cubed is a single dose that would contain 120 milligrammes of paracetamol.

So very well done if you managed to get that correct.

Great job, guys.

For part B then, we were asked to calculate the number of moles of paracetamol in a single dose to three significant figures.

So we need to use that mathematical relationship of moles as equal to the mass times the relative mass.

What we found out in part A that the mass in its standard unit of grammes is equal to 0.

120 grammes.

The relative mass then.

we need to calculate using the chemical formula for paracetamol, and that comes out at the answer of 151.

0 So if we take the values for the relative mass and the mass and put it into our relationship for moles to three significant figures, our final answer is 0.

000795.

Moles of paracetamol is found in a single dose of the children's medicine.

Fantastic work, guys.

You've done an amazing job.

Really, really impressive.

Wow, we have gone through a lot in today's lesson.

So let's just take a moment to summarise what we've learned.

Well, we've learned that the concentration of an aqueous solution is the mass of solute particles that have dissolved in a volume of solvent.

And that solvent is usually about one decimeter cube of distilled water, and that means the concentration would be expressed in grammes per decimeter cubed.

But we also know that the mass of one mole of a solute is going to be equal to the relative mass of that solute, but measured in grammes, which means then that concentration can be expressed in two ways, either grammes per decimeter cubed, or it could be expressed in moles per decimeter cubed.

We've also learned that equal volumes of solutions of the same concentration will have equal numbers of dissolved solute particles.

And we've also learned that the volume of our solvent and the mass of our solute can be expressed in a variety of units, but that we can easily convert between those units to the standard units that are needed to express and compare concentrations easily.

I hope you've had a good time learning with me.

I certainly have had a good time learning with you, and I hope to see you again soon.

Bye for now.