Stoichiometry
The quantitative study of the mass and mole relationships between reactants and products in a chemical reaction.
Formula / equation
n_A / a = n_B / b
Unit
mol
In depth
Stoichiometry rests entirely on the conservation of atoms expressed by a balanced equation. Every calculation follows the same route: convert the given quantity to moles, apply the mole ratio from the coefficients, then convert to the units the answer requires. It is what makes chemistry a predictive rather than descriptive science.
Examples in the real world
Calculating that 4.0 g of hydrogen needs 32.0 g of oxygen to form 36.0 g of water in 2H₂ + O₂ → 2H₂O.