STOICHIOMETRIC
CALCULATIONS
Lesson 4.3
WHAT IS STOICHIOMETRY?
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Stoichiometry refers to the quantitative
relationships between the substances that are
used up and produced in chemical reactions.
Stoichiometry is founded on the lawof
conservation of mass where the total mass of the
reactants equals to the total mass of the
products, leading to the insight that the relations
among the quantities of reactants and products
typically form a ratio of positive integers
AVOGADRO’S NUMBER
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Avogadro’s Number (6.022 x1023) was first coined
by physicist Jean Perrin, after the Italian
Scientist Amedeo Avogadro, who first proposed
that the volume of gas at a given time is
proportional to the number of atoms or molecules
regardless of the nature of the gas.
1 Mole = 6.022 x 1023 atoms, formula units,
molecules or ions
This equation gives the Molar Mass of the leemnt, expressed in
grams per mol (g/mol). Sometimes, the molar mass of an element
is termed atomic weight or atomic mass
2 atoms Fe x 55.85 g/mol Fe = 111.7 g/mol Fe
+ 3 atoms O x 16.00 g/mol O = 48.00 g/mol O
molar mass of Fe2O3
= 159.7 g/mol Fe2O3
Mass of
Product
Mass of
Reactant
Given: Balanced Equation, amount of reactant
Required: Amount of Product
Use Molar mass
of reactant
Mole of
Reactant
Use Molar mass
of Product
Use Molar Ratio from
Balanced equation
Mole of
Product