•

Updated Mar 14, 2026

•

3 pages

Quantitative Chemistry for GCSE AQA

Tara Vidal

@taravidal_jrny

Chemistry calculations might seem intimidating, but they're actually just straightforward... Show more

1 / 3

1. Relative atomic mass

Average mass of the isotopes that
element weighted to take into ac-
count the abundance of each iso-
tope

2. Relat

Relative Masses and the Moles Formula

Understanding relative atomic mass is your starting point for all chemistry calculations. It's simply the average mass of an element's isotopes, weighted by how common each isotope is in nature. Don't worry about memorising actual masses - you'll always get these from the periodic table.

The relative formula mass (Mr) works exactly the same way, but for compounds instead of single elements. Just add up all the relative atomic masses of every atom in the formula. Here's the crucial bit: ignore any big numbers at the front of formulas when calculating Mr.

Your most important formula to remember is: Number of moles = Mass (g) ÷ Mr or Ar. Think of it as the "moles triangle" - cover what you want to find, and the triangle shows you what to do with the other two values.

Key Tip: Neither relative atomic mass nor relative formula mass have units - they're just numbers you can read straight from your data sheet.

Reacting Masses and Concentration

Reacting masses calculations become simple when you think in moles first. The golden rule: if one mole reacts, one mole gets produced. Work out the moles of what you know, then convert back to mass for your answer.

Watch out for limiting reactants - these are the chemicals that get completely used up and stop the reaction. Any excess reactants just sit there doing nothing, so you can ignore them in your calculations.

Concentration tells you how much stuff is dissolved in a solution. You'll use two different units: g/dm³ $mass-based$ and mol/dm³ $moles-based$ . The formulas are concentration = mass ÷ volume and concentration = moles ÷ volume respectively.

Percentage yield compares what you actually got with what you theoretically could have got: (actual yield ÷ theoretical yield) × 100. It's always under 100% because reactions are never perfect in real life.

Remember: If your percentage yield is over 100%, you've definitely made a mistake somewhere!

Atom Economy and Gas Volumes

Atom economy measures how much of your starting materials actually becomes useful product. It's calculated as: (Mr of desired product ÷ Mr of all products) × 100. High atom economy means less waste, which saves money and helps the environment.

Companies love reactions with high atom economy because they're not throwing away expensive raw materials. It's all about sustainability and keeping costs down in industrial processes.

For gas volume calculations, there's a brilliantly simple formula: Volume (dm³) = moles × 24. This only works at room temperature and pressure, but that's usually what exam questions assume anyway.

When you're calculating masses using concentration in mol/dm³, work in two steps: first find moles using concentration × volume, then convert to mass using moles × Mr.

Pro Tip: Always check your units match up - if concentration is in mol/dm³, make sure volume is in dm³, not cm³!

We thought you’d never ask...

What is the Knowunity AI companion?

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.

Where can I download the Knowunity app?

You can download the app from Google Play Store and Apple App Store.

Is Knowunity really free of charge?

That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.

Most popular content in Chemistry

GCSE AQA Chemistry Topic 1

Quiz covering all of topic 1

Chemistry

BTEC Applied Science Unit 1 Overview

Comprehensive resource for Year 12 students pursuing a Level 3 Diploma in Applied Science. This booklet covers essential topics including cell structure, chemical properties, and wave theory, providing clear explanations and key concepts to aid in your studies and exam preparation.

Chemistry

A-level OCR A Chemistry summary sheets

Everything from snaprevise for OCR chemistry a-level

Chemistry

Quick Runthrough of Chemistry Paper 1

FOR FT HT COMBINED & HIGHER

Chemistry

GCSE Chemistry Revision Notes

AQA GCSE Combined Chemistry * detailed summary

Chemistry

AQA GCSE Chemistry 4.2 Bonding, structure and the Properties of Matter

4.2 Metals and Alloys

Chemistry

Essential Chemistry Practicals

Explore key AQA GCSE Chemistry practicals, including flame tests, titration, and gas identification. This resource covers essential techniques for analyzing ions, making salts, and understanding reaction kinetics. Perfect for students preparing for exams and practical assessments.

Chemistry

Redox Reactions Overview

Explore the fundamentals of redox reactions, including oxidation states, definitions of oxidation and reduction, and the roles of oxidizing and reducing agents. This summary covers key rules for determining oxidation states, the concept of disproportionation, and practical applications in chemical equations. Ideal for A-Level Chemistry students preparing for exams.

Chemistry

AQA GCSE Biology 4.1 Atomic structure and the Periodic Table

4.1 Mixtures

Chemistry

Most popular content

An Inspector Calls: Character Insights

Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.

English Literature

Sociology of Education Overview

Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.

Sociology

Comprehensive Crime & Deviance Overview

Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.

Sociology

Sociology of Families: Comprehensive Revision

Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.

Sociology

WJEC Unit 4 Criminology

Criminology unit 4 detailed revision note

Criminology

aqa higher tier combined science - biology b1 : cell biology, paper 1

b1: cell biology - paper 1

Biology

Criminology: Crime & Punishment Overview

Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.

Criminology

Macbeth: Guilt and Ambition

Explore the complex themes of guilt and ambition in Shakespeare's 'Macbeth'. This analysis covers key characters, including Macbeth and Lady Macbeth, their moral dilemmas, and the tragic consequences of their ambition. Ideal for students studying character motivations, thematic elements, and the psychological impact of power. Includes insights on the natural order, manipulation, and the descent into madness.

English Literature

AQA Biology: Key Concepts

Explore essential AQA Biology topics including Photosynthesis, Respiration, Homeostasis, Genetics, and Ecology. This comprehensive knowledge organizer covers key concepts such as energy transfer, hormonal control, and genetic variation, providing a solid foundation for your studies. Ideal for exam preparation and understanding biological processes.

Biology

Can't find what you're looking for? Explore other subjects.

Students love us — and so will you.

4.6/5

App Store

4.7/5

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 Knowunity AI. 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

Stefan S

iOS user

Samantha Klich

Android user

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Basil

Android user

David K

iOS user

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

Rohan U

Android user

Xander S

iOS user

Elisha

iOS user

Paul T

iOS user

Chemistry

•

513

•

Updated Mar 14, 2026

•

3 pages

Quantitative Chemistry for GCSE AQA

Tara Vidal

@taravidal_jrny

Chemistry calculations might seem intimidating, but they're actually just straightforward maths problems with atoms and molecules. Once you master a few key formulas and understand what relative masses and moles really mean, you'll breeze through these questions in your exams.

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

Relative Masses and the Moles Formula

Key Tip: Neither relative atomic mass nor relative formula mass have units - they're just numbers you can read straight from your data sheet.

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

Reacting Masses and Concentration

Remember: If your percentage yield is over 100%, you've definitely made a mistake somewhere!

Sign up to see the contentIt's free!

Access to all documents

Improve your grades

Join milions of students

Atom Economy and Gas Volumes

Companies love reactions with high atom economy because they're not throwing away expensive raw materials. It's all about sustainability and keeping costs down in industrial processes.

When you're calculating masses using concentration in mol/dm³, work in two steps: first find moles using concentration × volume, then convert to mass using moles × Mr.

Pro Tip: Always check your units match up - if concentration is in mol/dm³, make sure volume is in dm³, not cm³!