Stoichiometry game: moles, molar mass and limiting reactant
A chemistry game for learning stoichiometry by treating the balanced reaction as a recipe. The equation appears as tiles, with the coefficients in large type, the data under one substance and a «?» under the one you want. You calculate molar masses from atomic masses, convert grams to moles, use the coefficients to work out how many moles form or are needed, go from grams of one substance to grams of another, count particles with Avogadro’s number and, on the hard level, find the limiting reactant. The reactions are the textbook ones: forming water, burning methane and propane, making ammonia or decomposing limestone. When you answer, the gap fills in and the working is explained step by step.
Chemistry · Secondary, Sixth form
The most common stoichiometry mistake is reading 2 H₂ + O₂ → 2 H₂O as if it were grams. The game always makes you go through moles: grams to moles with the molar mass, one substance to another with the coefficients, and back to grams. You type the result, so there is no guessing between options: either you go through moles or it does not come out. And with the limiting reactant, besides saying which runs out, you work out how much of the other is left over.
With 3 mol of hydrogen and 2 of oxygen, hydrogen runs out first even though there is more of it: the recipe needs twice as much. When you answer, the game marks which reactant runs out and which is left over, which is what exam problems ask for.
Atomic masses are the rounded classroom values (H = 1, C = 12, O = 16…) and the molar mass answer shows the breakdown by atoms. You practise the reasoning, not the calculator, and the numbers come out exact.
"2 H₂ + O₂ → 2 H₂O appears with «8 g» under hydrogen and a «?» under water: how many grams of water form? The molar mass of H₂ is 2 g/mol, so 8 g is 4 mol. The recipe says 2 mol of H₂ give 2 mol of water, so 4 mol of water form. Water is 18 g/mol, so that is 4 · 18 = 72 g. Without going through moles you never reach 72."
Prefer to learn without screens? Try this analogue version:
Write the «recipe» for a sandwich: 2 slices of bread + 1 slice of cheese → 1 sandwich.
Imagine you have 10 slices of bread and 7 of cheese. How many sandwiches can you make, and what is left over?
Do the same with 2 H₂ + O₂ → 2 H₂O and 6 mol of H₂ with 5 mol of O₂.
Check that the limiting reactant is not always the one there is least of.
If you like The Chemical Recipe, these activities work similar skills:
The step before: balance the reaction before using it as a recipe.
Another chemistry game with moles: concentration, grams per litre and dilutions.
A chemistry game on ionic, covalent and metallic bonding.
More practice on · Chemistry
The Mole and Stoichiometry
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