Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

Stoichiometry Notes



The term stoichiometry is derived from two Greek words: stoicheion (meaning “element”) and metron (meaning “measure”).

Stoichiometry refers to the quantitative relationship among reactants and products in a chemical reaction that is represented through a chemical equation. 

Stoichiometry calculations are based on the Law of conservation of mass. Since atoms cannot be destroyed or created -through chemical reactions-, the number and kind of atoms before and after the reactions are always the same. 


Steps to resolve a stoichiometry problem

stoich steps


How many grams of potassium will be required to form 0.25g of Hydrogen gas through the following reaction?

2K   +   2H2O   →   2KOH   +   H2

Solution:  First we have to plan the step by step

stoich example1
stoichiometry example

In general, the steps are always the ones shown in the organizer below


For calculations, refer to the exercises in the videos below


 Theorethical yield, actual yield and % Yield.

Theoretical yield

The amount of product that could possibly be produced in a given reaction, calculated according to the starting amount of the limiting reagent.

Actual yield

The amount of product actually obtained in a chemical reaction.

Percent yield

Refers to the efficiency of a chemical reaction; defined as the   

% Yield =      actual yield      x 100     
                           theoretical yield 

This is an external video (not mine but very good!)