Transcript Stoichiometry

Stoichiometry is the study of the quantitative, or
measurable, relationships that exist in chemical
formulas and chemical reactions. (Calculations
that relate quantities of substances are known
as stoichiometry problems.)
The word stoichiometry derives from two Greek
words: stoicheion (meaning "element") and
metron (meaning "measure"). Stoichiometry
deals with calculations about the masses
(sometimes volumes) of reactants and products
involved in a chemical reaction. It is a very
mathematical part of chemistry, so be prepared
for lots of calculator use.
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Jeremias Benjaim
Richter (1762-1807) was
the first scientist to
introduce the principles
of stoichiometry.
In 1792 he wrote:
"Stoichiometry is the
science of measuring
the quantitative
proportions or mass
ratios in which chemical
elements stand to one
another.”
In a balanced equation, the coefficients
indicate the number of particles of each
substance taking part in the reaction. These
coefficients can be used to determine the ratio
of moles, or molar ratios. Molar ratios are
essential for solving any stoichiometry
problem.
CH4 + 2O2  CO2 + 2H2O
What is the molar ratio of CH4 to H2O?
What is the molar ratio of O2 to CO2?
What is the molar ratio of H2O to O2?
Mole-mole problems are problems where you
convert from moles of one substance to moles
of another substance. The ability to convert
moles of one substance in a reaction to moles of
another substance in a reaction is also essential
for solving more complex types of stoichiometry
problems.
How many moles of HCl are needed to react
with 2.3 moles of Zn?
2HCl + Zn  ZnCl2 + H2
(Moles of given x molar ratio)
1
2.3 mol Zn x _2_HCl____ = 4.6 mol HCl
1
1 Zn
Magnesium burns in oxygen to produce
magnesium oxide. How many moles of oxygen
are needed to burn 0.52 mole of magnesium?
2Mg + O2  2MgO
How many moles of Al(NO2)3 will be produced
when 0.75 mol AgNO2 reacts according to the
following equation:
3AgNO2 + Al  Al(NO2)3 + 3Ag