‹ Chemistry simulationsChemistry · AS Level 9701 · 2 Atoms, molecules and stoichiometrySeven simulations covering Topic 2: relative atomic mass from a mass spectrum, the mole and the Avogadro constant, empirical and molecular formulae, limiting reagents and reacting masses, the ideal gas equation and molar volume, a titration you carry out yourself, and percentage yield with atom economy.
A mass spectrometer sorts the isotopes of an element by mass and measures how much of each there is. The relative atomic mass is the abundance-weighted mean. Pick an element and read the calculation off the spectrum.
One mole of any substance contains 6.02 × 10²³ particles and has a mass in grams equal to its relative formula mass. Choose a substance, set a mass, and watch the count of particles change. The scene shows a tiny sample: each model stands for 5 × 10²¹ particles.
From percentage composition to a formula: divide each percentage by Ar to get moles, divide by the smallest, and scale to whole numbers. The molecular formula is a whole-number multiple of the empirical formula, fixed by Mr.
The balanced equation fixes the ratio in which substances react. Whichever reactant runs out first limits the amount of product; the other is in excess. Set the amounts, press React, and watch the bars.
One mole of any ideal gas occupies 24.0 dm³ at room temperature and pressure. The ideal gas equation links pressure, volume, amount and temperature. Move the sliders and watch the piston find the new volume.
25.0 cm³ of sodium hydroxide of unknown concentration is in the flask with phenolphthalein. Add hydrochloric acid of known concentration from the burette until the pink just disappears, then use n = cV and the 1 : 1 ratio to find the unknown.
Percentage yield compares what you actually made with the theoretical maximum. Atom economy asks what fraction of the reactant mass ends up in the product you want, and is fixed by the equation alone.
Relative atomic mass from a mass spectrum, the mole and the Avogadro constant in 3D, empirical and molecular formulae, limiting reagent bars, a 3D gas piston for pV = nRT and molar volume, an acid-base titration you carry out yourself, and percentage yield with atom economy.
Seven simulations covering Topic 2: relative atomic mass from a mass spectrum, the mole and the Avogadro constant, empirical and molecular formulae, limiting reagents and reacting masses, the ideal gas equation and molar volume, a titration you carry out yourself, and percentage yield with atom economy.
Atoms, molecules and stoichiometry is a free, browser-based simulation for Cambridge International AS & A Level Chemistry 9701 (topic 2 Atoms, molecules and stoichiometry). The same ideas are examined in Cambridge IGCSE Chemistry 0620 (topic 7 Acids, bases and salts, topic 12 Experimental techniques and chemical analysis, topic 3 Stoichiometry). The course is assessed in Paper 1 (Multiple Choice (AS)), Paper 2 (AS Structured), Paper 3 (Advanced Practical), Paper 4 (A Level Structured), Paper 5 (Planning, Analysis, Evaluation). Syllabus for examination in 2025-2027. There are 7 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.
Full syllabus map: AS Level Chemistry 9701 topic 2.
All simulation labs · AS Level Chemistry 9701 · TheLucidSTEM home