Subjects
Classic Dramatic Literature
Modern Lyric Poetry
Influential English-Language Authors
Classic and Contemporary Novels
Literary Character Analysis
Romantic and Love Poetry
Reading Analysis and Interpretation
Evidence Analysis and Integration
Author's Stylistic Elements
Figurative Language and Rhetoric
Show all topics
Human Organ Systems
Cellular Organization and Development
Biomolecular Structure and Organization
Enzyme Structure and Regulation
Cellular Organization Types
Biological Homeostatic Processes
Cellular Membrane Structure
Autotrophic Energy Processes
Environmental Sustainability and Impact
Neural Communication Systems
Show all topics
Social Sciences Research & Practice
Social Structure and Mobility
Classic Social Influence Experiments
Social Systems Theories
Family and Relationship Dynamics
Memory Systems and Processes
Neural Bases of Behavior
Social Influence and Attraction
Psychotherapeutic Approaches
Human Agency and Responsibility
Show all topics
Chemical Sciences and Applications
Chemical Bond Types and Properties
Organic Functional Groups
Atomic Structure and Composition
Chromatographic Separation Principles
Chemical Compound Classifications
Electrochemical Cell Systems
Periodic Table Organization
Chemical Reaction Kinetics
Chemical Equation Conservation
Show all topics
Nazi Germany and Holocaust 1933-1945
World Wars and Peace Treaties
European Monarchs and Statesmen
Cold War Global Tensions
Medieval Institutions and Systems
European Renaissance and Enlightenment
Modern Global Environmental-Health Challenges
Modern Military Conflicts
Medieval Migration and Invasions
World Wars Era and Impact
Show all topics
120
•
31 Dec 2025
•
Florence Thomas
@florencethomas_cxht
Mass spectrometry is a powerful analytical technique that scientists use... Show more
Ever wondered how scientists identify mystery substances? Mass spectrometry is like a molecular fingerprinting system that reveals exactly what's in a sample. The process starts by turning particles into ions (charged particles), then accelerating and deflecting them through the instrument.
The key to understanding mass spectrometry lies in the mass-to-charge ratio . Heavier isotopes have larger m/z values, so they follow wider curved paths when deflected. Since most ions carry a 1+ charge, the separation mainly depends on their mass.
Here's something interesting: if an ion picks up a 2+ charge instead of 1+, it gets deflected more because its m/z ratio is halved. The abundance stays the same, but the signal appears at a different position on the spectrum.
Quick Tip: Remember that doubling the charge halves the m/z ratio - this often catches students out in exam questions!
Sometimes you'll need to work backwards from the average relative atomic mass to find isotope percentages. This is easier than it looks once you know the method. Take bromine with isotopes of mass 79 and 81, and an average atomic mass of 79.908.
Set up the equation: if x% is ⁷⁹Br, then % must be ⁸¹Br. So: 79x + 81 = 7990.8. Expanding this gives: 79x + 8100 - 81x = 7990.8, which simplifies to -2x = -109.2.
Solving gives x = 54.6, meaning ⁷⁹Br is 54.6% and ⁸¹Br is 45.4%. The key is setting up the algebra correctly and remembering that percentages must add up to 100.
Exam Hack: Always check your percentages add to 100% - it's an instant way to spot calculation errors!
Relative isotopic mass compares the mass of one specific isotope to 1/12th of a carbon-12 atom. Think of carbon-12 as the universal reference point - like using metres to measure length. Relative atomic mass is the weighted average of all isotopes of an element.
Relative formula mass (RFM) is simply the sum of all atomic masses in a compound. For NH₃, you add nitrogen (14) plus three hydrogens (1+1+1) to get 17. For more complex compounds like Al₂(SO₄)₃, count each atom carefully: 2 aluminium, 3 sulphur, and 12 oxygen atoms.
Hydrated compounds like CuSO₄·5H₂O include water molecules in the calculation. The dot means the water is loosely attached, but you still count all the atoms when calculating the RFM.
Memory Trick: Write out each atom individually when calculating RFM - it prevents you from missing atoms in brackets!
Time of flight spectroscopy is the most common type of mass spectrometry you'll encounter. The entire apparatus operates under vacuum to prevent ions colliding with air molecules, which would mess up the results.
The process has three main stages: ionisation, acceleration, and ion drift. During ionisation, the sample dissolves in a volatile solvent and gets forced through a needle connected to high voltage. This creates tiny charged droplets that eventually become single positive ions.
All ions receive the same kinetic energy during acceleration, but heavier particles move slower than lighter ones. As ions travel down the flight tube, they separate based on their speed. The detector measures their arrival time and converts this into electrical signals.
Finally, a computer processes these signals to generate a mass spectrum - essentially a graph showing which masses are present and in what amounts. The whole system works because lighter ions reach the detector first.
Real-World Connection: Mass spectrometry is used everywhere from drug testing in sports to identifying explosives at airports!
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.
App 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
Florence Thomas
@florencethomas_cxht
Mass spectrometry is a powerful analytical technique that scientists use to identify unknown compounds and determine the composition of elements. It works by turning particles into ions, accelerating them, and measuring how they deflect based on their mass-to-charge ratio.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered how scientists identify mystery substances? Mass spectrometry is like a molecular fingerprinting system that reveals exactly what's in a sample. The process starts by turning particles into ions (charged particles), then accelerating and deflecting them through the instrument.
The key to understanding mass spectrometry lies in the mass-to-charge ratio . Heavier isotopes have larger m/z values, so they follow wider curved paths when deflected. Since most ions carry a 1+ charge, the separation mainly depends on their mass.
Here's something interesting: if an ion picks up a 2+ charge instead of 1+, it gets deflected more because its m/z ratio is halved. The abundance stays the same, but the signal appears at a different position on the spectrum.
Quick Tip: Remember that doubling the charge halves the m/z ratio - this often catches students out in exam questions!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Sometimes you'll need to work backwards from the average relative atomic mass to find isotope percentages. This is easier than it looks once you know the method. Take bromine with isotopes of mass 79 and 81, and an average atomic mass of 79.908.
Set up the equation: if x% is ⁷⁹Br, then % must be ⁸¹Br. So: 79x + 81 = 7990.8. Expanding this gives: 79x + 8100 - 81x = 7990.8, which simplifies to -2x = -109.2.
Solving gives x = 54.6, meaning ⁷⁹Br is 54.6% and ⁸¹Br is 45.4%. The key is setting up the algebra correctly and remembering that percentages must add up to 100.
Exam Hack: Always check your percentages add to 100% - it's an instant way to spot calculation errors!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Relative isotopic mass compares the mass of one specific isotope to 1/12th of a carbon-12 atom. Think of carbon-12 as the universal reference point - like using metres to measure length. Relative atomic mass is the weighted average of all isotopes of an element.
Relative formula mass (RFM) is simply the sum of all atomic masses in a compound. For NH₃, you add nitrogen (14) plus three hydrogens (1+1+1) to get 17. For more complex compounds like Al₂(SO₄)₃, count each atom carefully: 2 aluminium, 3 sulphur, and 12 oxygen atoms.
Hydrated compounds like CuSO₄·5H₂O include water molecules in the calculation. The dot means the water is loosely attached, but you still count all the atoms when calculating the RFM.
Memory Trick: Write out each atom individually when calculating RFM - it prevents you from missing atoms in brackets!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Time of flight spectroscopy is the most common type of mass spectrometry you'll encounter. The entire apparatus operates under vacuum to prevent ions colliding with air molecules, which would mess up the results.
The process has three main stages: ionisation, acceleration, and ion drift. During ionisation, the sample dissolves in a volatile solvent and gets forced through a needle connected to high voltage. This creates tiny charged droplets that eventually become single positive ions.
All ions receive the same kinetic energy during acceleration, but heavier particles move slower than lighter ones. As ions travel down the flight tube, they separate based on their speed. The detector measures their arrival time and converts this into electrical signals.
Finally, a computer processes these signals to generate a mass spectrum - essentially a graph showing which masses are present and in what amounts. The whole system works because lighter ions reach the detector first.
Real-World Connection: Mass spectrometry is used everywhere from drug testing in sports to identifying explosives at airports!
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
Dive into A-Level Chemistry with this comprehensive guide on mole calculations, including mole conversions, molar mass, and stoichiometry. This resource covers essential equations, practical examples, and detailed explanations to help you master the concepts of moles and their applications in gas volume and relative formula mass. Perfect for exam preparation and enhancing your understanding of quantitative chemistry.
ChemistryExplore essential calculations and concepts related to moles in chemistry. This summary covers molar mass, concentration, ideal gas equations, empirical and molecular formulas, and the significance of atom economy in chemical processes. Ideal for A-Level Chemistry students seeking to master the topic of 'Amount of Substance'.
ChemistryExplore the principles of mass spectrometry, including the calculation of relative atomic mass and the significance of isotopes. This summary covers key concepts such as isotopic mass, relative abundance, and the impact of vacuum conditions on ion behavior. Ideal for chemistry students preparing for exams.
ChemistryExplore key concepts in chemistry calculations, including relative atomic mass, moles, concentration, and molar mass. This summary provides essential formulas and methods for calculating percentage composition and average rates of reaction, tailored for students preparing for exams.
ChemistryExplore the principles of mass spectrometry, including molecular fragmentation, mass spectra interpretation, and relative abundance analysis. This summary provides essential insights for AQA A-Level organic chemistry, helping students understand how to deduce molecular structures and identify compounds through mass spectrometry techniques.
ChemistryExplore key concepts in physical chemistry, including relative atomic and molecular mass, Avogadro's constant, the ideal gas equation, empirical and molecular formulas, percentage yield, and atom economy. This summary provides essential calculations and principles for mastering mole concepts and stoichiometry.
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
English Literature
Biology
Sociology