Stoichiometry
We are going to be looking at Stoichiometry in this unit, as
well as the Mole and mole calculations for solids, liquids, and
gases.
• Stoichiometry is a section of chemistry that involves using
relationships that exist between reactants and/or products in a
chemical reaction to determine desired quantitative data.
• In Greek, stoikhein means element and metron means measure, so
stoichiometry literally translated means the measure of elements.
• In order to use stoichiometry to run calculations about chemical
reactions, it is important to first understand the relationships that
exist between products and reactants and why they exist, which
require understanding how to balanced reactions.
• Think of chemical reactions, or equations, as
being like recipes – we add things (reactants)
together to get the finished product.
• This is why you learned about balancing
equations last week. The coefficients used to
balance equations are called stoichiometric
coefficients.
• They tell us the ratios that apply to the
reactants and the products.
• Almost any quantitative relationship can be
converted into a stoichiometric ratio – as we
will see.
Moles
• This is a mole
• Just kidding – this is not the Mole we are
going to be discussing in this course.
• The Mole we use in Chemistry is a unit of
measurement and is defined as the amount of
any substance that contains as many
elementary entities (e.g. atoms, molecules,
electrons, and ions) as there are in exactly 12
grams of pure Carbon-12 (the isotope of
Carbon with the relative atomic mass of 12).
• This corresponds to Avogadro’s number, which
has the value of 6.023 x 1023.
• The mole is a base unit of the SI system and
has a unit symbol mol
Some history
• Amedeo Avogadro was an Italian scientist who, in
1811, first proposed that the volume of a gas (at
a given temperature and pressure) is proportional
to the number of atoms or molecules of that gas.
• Jean Perrin, a French physicist, proposed in 1909
the constant should be named in honour of
Avogadro. Perrin won the Nobel Prize in Physics
in 1926 for his work in determined the Avogadro
constant by several different methods.
• Accurate determinations of Avogadro's number require
the measurement of a single quantity on both the
atomic and macroscopic scales using the same unit of
measurement.
• This became possible for the first time when American
physicist Robert Millikan measured the charge of an
electron in 1910.
• The electric charge per mole of electrons is a constant
called the Faraday constant when, in 1834, Robert
Faraday published his work on electrolysis.
• By dividing the charge of a mole of electrons by the
charge of a single electron the value of Avogadro’s
number is obtained.
• Avogadro’s number is the center core of Chemistry –
much like Evolution is the central tenet of Biology.
How big is 6.023x1023???
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You have a single little smartie.
It doesn’t look like much, does it?
Now take 6.023x1023 of the little buggers.
How much room would a mole of smarties
occupy?
• If you could count 10 every second, how long
would it take to count them all?
MOLE CALCULATIONS FOR SOLIDS