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Britain & the wider world: 1745 -1901
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Chemistry
5 Dec 2025
461
4 pages
Skylar Vickerman @skylarvickerman_vqfq
Ever wondered how chemists measure incredibly tiny atoms and molecules? They use a special unit called the mole... Show more
The mole is chemistry's way of counting atoms, molecules, and ions - much like how we use "dozen" to count eggs. One mole of any substance always contains exactly the same number of particles, whether you're talking about sodium atoms or water molecules.
This magic number is called Avogadro's constant 6.02 × 10²³ particles per mole. It's absolutely huge - imagine writing out 602 followed by 21 zeros!
Here's what this means practically one mole of sodium contains 6.02 × 10²³ sodium atoms, whilst one mole of water contains 6.02 × 10²³ water molecules. The particles are different sizes, but the count is identical.
Quick Check Remember that moles can count anything - atoms, molecules, ions, or even formula units. It's all about that constant number!
Here's where moles become really useful one mole of any element weighs exactly its atomic mass in grams. This weight is called the molar mass.
Carbon has an atomic mass of 12, so one mole of carbon atoms weighs exactly 12g. Helium's atomic mass is 4, so one mole of helium weighs 4g. See the pattern?
For compounds like water (H₂O), you simply add up the atomic masses (2 × 1) + 16 = 18g per mole. This connection between atomic mass and molar mass is your key to solving chemistry problems.
Top Tip The atomic mass on the periodic table tells you directly how much one mole of that element weighs in grams!
In the lab, you'll weigh chemicals in grams but need to think in moles for reactions. That's where this essential formula comes in Mass = Moles × Molar Mass.
You can rearrange this triangle to find any missing value. Need moles? Divide mass by molar mass. Need molar mass? Divide mass by moles. The triangle makes it dead simple.
This formula is your best friend for converting between the practical world of grams and the theoretical world of moles. Master this, and you'll breeze through calculation questions.
Memory Aid Think "M&M" - Mass equals Moles times Molar mass!
Let's see the formula in action. Finding the mass of 0.250 moles of zinc? Zinc's atomic mass is 65, so 0.250 mol × 65 g/mol = 16.25g. Simple multiplication!
Going the other way is just as straightforward. With 2.64g of sucrose , divide to find moles 2.64g ÷ 342.3 g/mol = 7.71 × 10⁻³ mol.
Notice how the units cancel out perfectly? That's your check that you've set up the calculation correctly. Get comfortable with these conversions, and you'll tackle any moles question with confidence.
Exam Success Always check your units cancel properly - it's the easiest way to spot calculation errors!
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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definition of molar mass, how to calculate, examples included
ChemistrySI units, base units, derived units, metric conversion, the mole, dimensional analysis
ChemistryThis note helps simplify the definition of a mole, how to find molar mass, and how to use conversion factors.
ChemistryLearn about the fundamental units of the metric system and how to convert between different temperatures and measurements.
ChemistryExploring the properties of energy and how it travels through space using wave properties and equations related to periodic table and electron configuration. As well as period trends…
AP ChemistryUnit 2: Structure of the Atom
ChemistryApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Skylar Vickerman
@skylarvickerman_vqfq
Ever wondered how chemists measure incredibly tiny atoms and molecules? They use a special unit called the mole - think of it as a chemist's dozen, but instead of 12 items, one mole contains a massive 6.02 × 10²³ particles!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The mole is chemistry's way of counting atoms, molecules, and ions - much like how we use "dozen" to count eggs. One mole of any substance always contains exactly the same number of particles, whether you're talking about sodium atoms or water molecules.
This magic number is called Avogadro's constant: 6.02 × 10²³ particles per mole. It's absolutely huge - imagine writing out 602 followed by 21 zeros!
Here's what this means practically: one mole of sodium contains 6.02 × 10²³ sodium atoms, whilst one mole of water contains 6.02 × 10²³ water molecules. The particles are different sizes, but the count is identical.
Quick Check: Remember that moles can count anything - atoms, molecules, ions, or even formula units. It's all about that constant number!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Here's where moles become really useful: one mole of any element weighs exactly its atomic mass in grams. This weight is called the molar mass.
Carbon has an atomic mass of 12, so one mole of carbon atoms weighs exactly 12g. Helium's atomic mass is 4, so one mole of helium weighs 4g. See the pattern?
For compounds like water (H₂O), you simply add up the atomic masses: (2 × 1) + 16 = 18g per mole. This connection between atomic mass and molar mass is your key to solving chemistry problems.
Top Tip: The atomic mass on the periodic table tells you directly how much one mole of that element weighs in grams!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
In the lab, you'll weigh chemicals in grams but need to think in moles for reactions. That's where this essential formula comes in: Mass = Moles × Molar Mass.
You can rearrange this triangle to find any missing value. Need moles? Divide mass by molar mass. Need molar mass? Divide mass by moles. The triangle makes it dead simple.
This formula is your best friend for converting between the practical world of grams and the theoretical world of moles. Master this, and you'll breeze through calculation questions.
Memory Aid: Think "M&M" - Mass equals Moles times Molar mass!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Let's see the formula in action. Finding the mass of 0.250 moles of zinc? Zinc's atomic mass is 65, so: 0.250 mol × 65 g/mol = 16.25g. Simple multiplication!
Going the other way is just as straightforward. With 2.64g of sucrose , divide to find moles: 2.64g ÷ 342.3 g/mol = 7.71 × 10⁻³ mol.
Notice how the units cancel out perfectly? That's your check that you've set up the calculation correctly. Get comfortable with these conversions, and you'll tackle any moles question with confidence.
Exam Success: Always check your units cancel properly - it's the easiest way to spot calculation errors!
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
3
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
definition of molar mass, how to calculate, examples included
ChemistrySI units, base units, derived units, metric conversion, the mole, dimensional analysis
ChemistryThis note helps simplify the definition of a mole, how to find molar mass, and how to use conversion factors.
ChemistryLearn about the fundamental units of the metric system and how to convert between different temperatures and measurements.
ChemistryExploring the properties of energy and how it travels through space using wave properties and equations related to periodic table and electron configuration. As well as period trends…
AP ChemistryUnit 2: Structure of the Atom
ChemistryApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Sociology