Stoichiometry is chemistry’s accounting system: it tracks exactly how many atoms and molecules take part in a reaction. It rests on the mole — a fixed count of particles (6.022 × 10²³) that lets us weigh out atoms we can never see. MoleForge turns this famously hard, abstract topic into a factory you run: build molecules atom-by-atom, then balance live reactions so mass is conserved. Learn it by doing, from Class 9 formulas to Class 11–12 balancing and yield.
Almost every quantitative chapter that follows — thermochemistry, equilibrium, electrochemistry, titrations — assumes you can reason in moles. Master this one topic and the rest of chemistry starts to add up, literally.
The small number in H₂O means one water molecule has 2 hydrogen and 1 oxygen atom — a fixed recipe that never changes.
The big number in front, like the 2 in 2H₂O, multiplies the WHOLE molecule. Balancing only ever changes coefficients.
Atoms are never created or destroyed in a reaction, so each element must total the same on both sides of the arrow.
A mole is 6.022 × 10²³ particles — the bridge that lets us convert between grams we can weigh and atoms we cannot see.
One reactant runs out first and caps how much product forms; percent yield measures how efficient a real reaction is.
Fertiliser, fuel, medicine and clean water are all made by getting the stoichiometry exactly right, at industrial scale.
Every compound has a fixed formula — H₂O, CO₂, NH₃ — that tells you precisely which atoms, and how many of each, are locked inside one molecule. Reading those subscripts correctly is the first skill of the whole topic, and the reason a game that lets you physically build the molecule beats memorising it.
When substances react, atoms only rearrange — none appear or vanish. So a correct equation must have equal atoms of every element on both sides. You achieve that by choosing coefficients (how many of each molecule react), never by editing a subscript, which would change the substance itself. This is the single most common place students slip.
We cannot count 10²³ atoms one by one, so chemists group them into moles. A balanced equation’s coefficients are really mole ratios: “2 moles of H₂ react with 1 mole of O₂.” Combined with molar mass, that lets you predict exactly how many grams of product a reaction will make.
In practice one ingredient usually runs out first — the limiting reagent — and no reaction gives 100% of its theoretical product. Tracking the limiting reagent and percent yield is how industry decides what to buy, how much to make and how to cut waste.
Conservation of mass: a balanced equation has equal atoms of every element on both sides.
Turn the concepts above into a skill — play the game and get instant feedback.