Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

Stoichiometry Notes

Stoichiometry

Definition:

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

Example:

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

2K   +   2H2O   →   2KOH   +   H2

Solution: 

stoich example1

ANOTHER METHOD TO RESOLVE THE PROBLEMS

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!)