GCSE & A level chemical calculations notes and practise questions

INDEX of CALCULATIONS IN CHEMISTRY and quantitative chemical analysis notes and quizzes

[Author ©  Dr Phil Brown PhD: Doc Brown's exam revision notes suitable for students of GCSE level chemistry and advanced level pre-university/college chemistry courses: teach yourself chemical calculations - INDEX of ALL revision notes [updated Mar 21st 2026 *]

CHEMICAL CALCULATIONS INDEX PAGES of Online Quantitative Chemistry Calculations

INDEX OF CALCULATION QUIZZES

Links to Teaching and learning NOTES of EXAMPLES of types of chemical calculations

Some questions-quizzes are only for Advanced level are indicated

Many of these pages will help with UK based GCSE, IGCSE, O level chemistry courses and UK advanced level students (US grade 11-12 K12 AP Honors courses)

GCSE level QUIZ abbreviations: FT = Foundation Tier Quiz, HT = Higher Tier Quiz (harder)

3sf means give your answer to three significant figures etc.

1dp means give your answer to one decimal place etc.

TOP OF PAGE

1. What is relative atomic mass? Calculating relative atomic mass from % of  isotopes

See also Mass Spectrometer and A_r and relative isotopic mass

Quiz 1. on calculating relative atomic mass

Exam practice questions on relative atomic mass (A_r)  calculations

2. Calculating relative formula/molecular mass (M_r) of a compound or element molecule

QUIZ 2 on calculating relative formula/molecular mass

Exam practice questions on relative formula or molecular mass calculations

.3. Law of Conservation of Mass experiments reacting mass calculations

QUIZ 3. on Law of Conservation of Mass and simple reacting mass calculations

Section 3. does NOT involve using moles in calculations

Exam practice questions on the law of conservation of mass, simple reacting mass calculations

4. Calculating composition by percentage (%) mass of elements in a compound and other % composition calculations

Quiz 4 on % composition by mass

Exam practice questions on calculating the % composition of components in a compound

5. Calculating empirical formula and formula mass of a compound from reacting masses

Section 5. is an easy start, NOT using moles.

Quiz 5 on the basics of empirical formula

Exam practice questions on calculating an empirical/formula mass from reacting masses

6a. Reacting mass ratio calculations of reactants and products and brief mention of actual percent % yield and theoretical yield, atom economy and formula mass determination

 (NOT using moles, but still based on the law of conservation of mass)

See sections 14.2a and 14.2b for more detailed notes on actual/theoretical % yield and atom economy.

QUIZ 6 on reacting mass ratio calculations of reactants and products

Exam practice questions on reacting mass ratios, % yield and atom economy

6b. Reacting masses, concentration of solution and volumetric titration calculations

(These calculations do NOT using moles)

7. Introducing moles: The connection between moles, mass and formula mass - the basis of reacting mole ratio calculations (relating reacting mass and formula mass)

AND introducing the Avogadro constant

AND includes interpreting and deducing balanced chemical equations from the moles involved

Quiz 7 on the basics of moles, mass and formula mass

Exam practice questions on relating mass, formula mass and moles and reacting mole ratio calculations from a given chemical equation

Also extra more advanced Q's for Advanced Chemistry Students using the Avogadro Constant

and with worked out answers provided

8. Using moles to calculate empirical formula and deduce molecular formula of a compound/molecule (starting with reacting masses or % composition)

Quiz 8.on deducing an empirical and molecular formula using mole concept

Practice exam questions on calculating empirical or molecular formula using the mole concept

9. Moles and the molar volume of a gas, Avogadro's Law

Quiz 9 on moles and the molar volume of a gas, Avogadro's Law

Practice exam questions on calculating quantities of gases using the mole concept

10. Reacting gas volume ratios, Avogadro's Law and Gay-Lussac's Law (ratio of gaseous reactants-products)

Quiz 10. Calculations involving gas volume ratios in reactions

Practice exam questions on calculating ratios of reacting gas volumes and products.

11. Molarity, volumes and solution concentrations (and diagrams of apparatus)

Quiz 11 on the basics of molarity and solution concentrations

Practice exam questions on calculating molarity and masses from/for a given concentration

12. Volumetric titration procedures and calculations e.g. acid-alkali titrations (and diagrams of apparatus and descriptions of procedures) (introduction and sub-index for 9 sections)

Quiz 12 on the basics of acid-alkali titration calculations

Practice exam questions on titrations and working with molarities

See also Advanced level acid-base titration calculation questions (with answers)

and Advanced level REDOX titration calculation questions (with answers)

13. Electrolysis products calculations (e.g ratio of negative cathode and positive anode products)

Quiz 13. Electrolysis products calculations of ratio of cathode and anode products)

Practice exam questions on calculating the products from an electrolysis process

14. Other miscellaneous calculations e.g. % purity, % percentage & theoretical yield, atom economy, volumetric titration apparatus, dilution of solutions (and diagrams of apparatus), water of crystallisation, quantity of reactants required

14.1 % purity of a product calculations

14.2a % reaction yield and theoretical yield calculations, why can't get 100% yield

14.2b atom economy calculations

14.3 dilution of solutions calculations

14.4 water of crystallisation calculations

14.5 What quantity of chemicals are needed to carry out a reaction? calculation of quantities required and limiting quantity of a reactant (some examples use the mole concept too)

Calculations involving gases - Boyle's Law and Charles/Gay-Lussac Law - all about PVT etc.

The notes and questions indexed below are for UK Advanced A/AS level students only (US grade 11-12 K12 honors) level AND These students also need to be able to do everything indexed above!

15. Energy transfers in physical/chemical changes, activation energies and reaction profiles etc. (These notes are on a separate web page in the 'energy' section)

15. Energy transfers - GCSE easier foundation level questions

or Energy transfers - GCSE harder higher level questions

More enthalpy calculations explained for Advanced Level

Advanced A Level: Enthalpy Calculations with worked out answers

16. Gas calculations involving PVT relationship (Ideal Gas Equation) and determining molecular mass of a volatile liquid, but only practice examples in notes

17 Radioactivity and half-life calculations including dating materials

18. Selection of 9 Advanced A Level Practical Exercises and Calculations involving Volumetric Analysis and Gravimetric Analysis

More advanced topics on the ideal gas laws - various calculations including molecular mass determination, partial pressures and Graham's law of diffusion, kinetic particle model–theory and ideal and non–ideal real gas behaviour

Extra Advanced A Level Chemistry Calculations Exercises

e.g. for UK GCE-A-AS-A2 level, IB, US grades 11-12, US AP honors students)

(but all the basics you need to know are listed above)

Ideal gas law P-V-T calculations

Acid-base and other non-redox titration questions

Redox volumetric titration questions

molecular equilibrium problem solving

partition and solubility product calculations

pH-pK_a/b acid-base Q's and buffer pH calculations

Relative atomic mass calculations and mass spectrometer

Combined 'bumper' on-line Chemical Calculations Quizzes for UK KS4-GCSE-IGCSE-A level students of chemistry (US grade 9-12) (Based on sections Ex. 1 to 13 in the notes index above)

Basic GCSE Foundation level Quiz based on Ex. 2. to 6. (multiple choice and no moles)

More advanced GCSE higher level Quiz based on Ex. 1. to 13. (multiple choice with lots of moles)

Basic GCSE Foundation level Quiz based on Ex. 2. to 6. (type in answer and no moles)

More advanced GCSE higher level Quiz on Ex. 1. to 13. (lots of moles!)

Part 1 Introduction to chemical testing, analysing substances & line spectra

Part 2 Qualitative tests to identify organic molecule functional groups

Part 3 TESTS for cations (positive ions) and metal carbonates

Part 4 TESTS for gases, water and non–metallic elements

Part 5 TESTS for Anions (negative ions) including hydroxide (alkalis)

Combined 'bumper' on-line Chemical Calculations Quizzes for UK KS4-GCSE-IGCSE-A level students of chemistry (US grade 9-12) (Based on sections Ex. 1 to 13 in the notes index above)

Basic GCSE Foundation level Quiz based on Ex. 2. to 6. (multiple choice and no moles)

More advanced GCSE higher level Quiz based on Ex. 1. to 13. (multiple choice with lots of moles)

Basic GCSE Foundation level Quiz based on Ex. 2. to 6. (type in answer and no moles)

More advanced GCSE higher level Quiz on Ex. 1. to 13. (lots of moles!)

Quantitative Chemical Calculations (GCSE/IGCSE Chemistry)

Core Calculation Skills (common to all GCSE exam boards)

Students must be able to:

• Convert between mass, moles, and molar mass.
• Use Avogadro’s constant to calculate particles in a substance.
• Apply balanced chemical equations to determine mole ratios.
• Calculate concentration in mol/dm³ and g/dm³.
• Perform titration calculations (using volumes and concentrations).
• Work with percentage yield and atom economy.
• Identify limiting reagents in reactions.
• Calculate empirical and molecular formulae from data.
• Use gas volume relationships (molar gas volume at RTP).
• Apply reacting mass calculations to predict product amounts.

Exam Board-Specific Emphases

WJEC GCSE Chemistry

• Concentration calculations in mol/dm³ and g/dm³.
• Titration-based problem solving.
• Percentage yield and atom economy.
• Gas volume calculations (24 dm³ per mole at RTP).
• Empirical formula determination from experimental data.

CCEA GCSE Chemistry

• Mass–mole–formula triangle calculations.
• Conversion between cm³ and dm³ in concentration problems.
• Reacting mass problems using balanced equations.
• Percentage yield and atom economy.
• Gas volume calculations.
• Empirical formula from combustion or experimental data.

CIE Cambridge IGCSE Chemistry

• Mole calculations from mass, volume, and concentration.
• Titration calculations with balanced equations.
• Gas laws and molar volume at RTP.
• Empirical and molecular formulae.
• Percentage yield and purity.
• Stoichiometric calculations involving limiting reagents.

AQA GCSE Chemistry

• Mass–mole–concentration calculations.
• Titration calculations (including stepwise method).
• Percentage yield and atom economy.
• Limiting reactant problems.
• Gas volume calculations.
• Empirical formula from experimental data.
• Converting between mol/dm³ and g/dm³.

Edexcel GCSE Chemistry

• Mole calculations from mass, concentration, and gas volume.
• Titration calculations with balanced equations.
• Percentage yield and atom economy.
• Limiting reagent calculations.
• Empirical and molecular formulae.
• Gas volume calculations at RTP.
• Reacting mass problems linked to industrial chemistry contexts.

OCR Gateway Science Suite GCSE Chemistry

• Mole calculations from mass and concentration.
• Titration calculations with practical emphasis.
• Percentage yield and atom economy.
• Gas volume calculations.
• Empirical formula determination.
• Limiting reagent problems.

OCR 21st Century GCSE Chemistry

• Mole calculations from mass, concentration, and gas volume.
• Titration calculations with explanation of steps.
• Percentage yield and atom economy.
• Empirical formula from experimental data.
• Limiting reagent calculations.
• Gas volume relationships.

Exam Preparation Focus for GCSE level chemical calculations

• Unit conversions: cm³ ↔ dm³, g ↔ mol.
• Balanced equations: always the starting point for mole ratio problems.
• Methodical working: show steps clearly for partial credit.
• Conceptual understanding: not just plugging into formulas—students must explain reasoning in some boards (OCR 21st Century, WJEC).
• Cross-board overlap: all boards require mastery of mole calculations, titration, yield, atom economy, and empirical formulae.

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