STOICHIOMETRY TUTORIAL

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STOICHIOMETRY TUTORIAL

• Paul Gilletti

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Instructions This is a work along tutorial.
Each time you click the mouse or touch the space
bar on your computer, one step of the problem
solving occurs. Pressing the PAGE UP key will
backup the steps.
Get a pencil and paper, a periodic table and a
calculator, and lets get to work.
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(1-2-3) General Approach For Problem Solving
1. Clearly identify the Goal or Goals and the
UNITS involved. (What are you trying to do?)
2. Determine what is given and the UNITS.
3. Use conversion factors (which are really
ratios) and their UNITS to CONVERT what is given
into what is desired.
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Converting grams to moles.
Determine how many moles there are in 5.17 grams
of Fe(C5H5)2.
Goal
Given
units match
5.17 g Fe(C5H5)2
moles Fe(C5H5)2
0.0278
Use the molar mass to convert grams to moles.
Fe(C5H5)2
2 x 5 x 1.001 10.01
2 x 5 x 12.011 120.11
1 x 55.85 55.85
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Stoichiometry (more working with ratios)
Ratios are found within a chemical equation.
2HCl Ba(OH)2 ? 2H2O BaCl2
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coefficients give MOLAR RATIOS
2 moles of HCl react with 1 mole of Ba(OH)2 to
form 2 moles of H2O and 1 mole of BaCl2
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Mole Mole Conversions
When N2O5 is heated, it decomposes
2N2O5(g) ? 4NO2(g) O2(g)
a. How many moles of NO2 can be produced from 4.3
moles of N2O5?
2N2O5(g) ? 4NO2(g) O2(g)
4.3 mol
? mol
Units match
4.3 mol N2O5
moles NO2
8.6
b. How many moles of O2 can be produced from 4.3
moles of N2O5?
2N2O5(g) ? 4NO2(g) O2(g)
4.3 mol
? mol
4.3 mol N2O5
mole O2
2.2
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gram ? mole and gram ? gram conversions
When N2O5 is heated, it decomposes
2N2O5(g) ? 4NO2(g) O2(g)
a. How many moles of N2O5 were used if 210g of
NO2 were produced?
2N2O5(g) ? 4NO2(g) O2(g)
210g
? moles
Units match
210 g NO2
moles N2O5
2.28
b. How many grams of N2O5 are needed to produce
75.0 grams of O2?
2N2O5(g) ? 4NO2(g) O2(g)
75.0 g
? grams
75.0 g O2
grams N2O5
506
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Gram to Gram Conversions
Aluminum is an active metal that when placed in
hydrochloric acid produces hydrogen gas and
aluminum chloride. How many grams of aluminum
chloride can be produced when 3.45 grams of
aluminum are reacted with an excess of
hydrochloric acid?
Al(s) HCl(aq) ? AlCl3(aq)
H2(g)
2 6 2
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First write a balanced equation.
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Gram to Gram Conversions
Aluminum is an active metal that when placed in
hydrochloric acid produces hydrogen gas and
aluminum chloride. How many grams of aluminum
chloride can be produced when 3.45 grams of
aluminum are reacted with an excess of
hydrochloric acid?
Al(s) HCl(aq) ? AlCl3(aq)
H2(g)
2 6 2
3
? grams
3.45 g
Now lets get organized. Write the information
below the substances.
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gram to gram conversions
Aluminum is an active metal that when placed in
hydrochloric acid produces hydrogen gas and
aluminum chloride. How many grams of aluminum
chloride can be produced when 3.45 grams of
aluminum are reacted with an excess of
hydrochloric acid?
Al(s) HCl(aq) ? AlCl3(aq)
H2(g)
2 6 2
3
? grams
3.45 g
Units match
3.45 g Al
g AlCl3
17.0
Lets work the problem.
We must always convert to moles.
Now use the molar ratio.
Now use the molar mass to convert to grams.
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