Stoichiometry

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in chemical reactions. It relies on the mole concept and balanced equations to relate amounts of substances involved in a process.

A balanced chemical equation expresses the exact proportions in which substances react. The coefficients give the mole ratios, and molar masses convert between grams and moles. For gases at the same temperature and pressure, equal amounts of substance (in moles) occupy equal volumes, linking amounts to volumes.

To perform a stoichiometric calculation, follow these steps: (1) write and balance the equation; (2) convert known quantities to moles using molar masses; (3) use the appropriate mole ratios to find the moles of the desired substance; (4) convert the result to the desired units.

Example: in the reaction 2 H2 + O2 → 2 H2O, starting with 5 moles of H2 and 2 moles of O2, oxygen is the limiting reagent. The theoretical yield is 4 moles of H2O, and the actual yield is compared to this value to determine percent yield.

Stoichiometry also addresses concepts such as limiting reagents, theoretical yield, actual yield, and percent yield, and it emphasizes limitations such as measurement error, incomplete reactions, and side reactions that can affect the outcome of a process.