Transcript Stoichiometry

Daily Science Feb
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You are heating copper sulfate in the lab. The mass
of your test tube is 13.091g. You add 0.498 g of
CuSO4 to the test tube and re-mass the test tube
plus the copper sulfate. Your new mass is 13.575 g.
After heating the substance for 5 minutes you let it
cool and re-mass. The final mass is 13.400 g. What
is the formula for the hydrate?
STOICHIOMETRY
Pg. 79
Stoichiometry
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Chemical reactions stop when one of the reactants
has been completely used
As a scientists, we need to know how much that is
Or we might need to know how much product will
be made
Stoichiometry tells us this
Stoichiometry: The study of quantitative
relationships between amounts of reactants used
and products formed
Mole to mass relationships in chemical
reactions
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Coefficients in an equation tell you how many moles
there are of each element
4
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Fe(s) + 3 O2  2Fe2O3 (s)
You can calculate the grams of reactants and
products by using stoichiometry (dimensional
analysis)
Start with the number of moles of the element and
convert to mass using molar mass
Accounts for conservation of mass
Practice Moles to mass
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N2 (g) + 3 H2 (g)  2NH3 (g)
Mole to mole ratios
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Use the relationships between coefficients to write
conversion factors; called mole ratios
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Fe(s) + 3 O2  2Fe2O3 (s)
To determine how many mole ratios you can make,
multiply the number of reactants and products by
the next lowest number
Practice Mole to Mole ratios
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2Al (s) + 3 Br2 (l)  2AlBr3 (s)
Using Stoichiometry – Mole to mole
conversions
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You must begin with a BALANCED chemical equation
You are given the amount of moles of a substance
and you want to know how much of the other
reactant you need or how much product will be
formed
Start with the given and use mole to mole ratios
 Given
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unit goes on bottom! Desired on top!
Ex. How many moles of hydrogen gas will be
produced if you use 0.567 mol of potassium
 2K
(s) + 2 H2O (l)  2KOH (aq) + H2 (g)
Practice using mole to mole conversions
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How many moles of carbon dioxide are produced
when 11.0 moles of propane (C3H8) are burned?
 C3H8
(g) + O2 (g)  CO2 (g) + H2O (l)
Pg. 80
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Practice problems pg. 356 1 c-e
Practice problems pg. 357 2 c and 3 a
Practice Problems pg. 359 9 and 10