Chemistry – Stoichiometry Notes
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Stoichiometry:
Using the amount of one substance in a reaction to determine the amount of another substance in a reaction
Balanced reactions support the Law of ____________________________________
Once an equation is balanced, one can determine the ___________ ratio of the reactants and/or products.
Example 1 – Determining Mole Ratios
___ H2 + ___ O2  ___ H2O
Step 1: Balance.
Step 2: Determine the following mole ratios.
H2/O2 --------------------
H2/H2O
--------------------
O2/H2O
--------------------
O2/H2 --------------------
H2O/H2
--------------------
H2O/O2
--------------------
Mole ratios & significant figures: _______________________________________________________________
Review:
particles ——— moles ——— mass (g)
Stoichiometry Conversions:
moles A ——— moles B
Chemistry – Stoichiometry Notes
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Example 2 – Moles A to Moles B Conversions
___ H2 + ___ O2  ___ H2O
To produce 4.00 moles of H2O, how many moles of H2 are needed?
___ Zn + ___ HCl  ___ ZnCl2 + ___ H2
5.00 moles of HCl and excess Zn produce how many moles of ZnCl2?
Excess: ____________________________________________________________________________________
Example 3 – Moles A to Particles B
___ H2 + ___ O2  ___ H2O
3.00 moles of O2 and excess H2 produce how many molecules of H2O?
___ Zn + ___ HCl  ___ ZnCl2 + ___ H2
How many molecules of HCl are needed to produce 7.00 moles of ZnCl2?
Chemistry – Stoichiometry Notes
Example 4 – Particles A to Moles B
___ H2 + ___ O2  ___ H2O
8.24 x 1022 molecules of O2 will react completely with how many moles of H2?
___ Zn + ___ HCl  ___ ZnCl2 + ___ H2
7.11 x 1023 atoms of Zn will react with excess HCl to produce how many moles of H2?
Example 5 – Moles A to Mass (g) B
___ H2 + ___ O2  ___ H2O
What mass, in grams, of O2 is needed to produce 1.00 mole of H2O?
___ Zn + ___ HCl  ___ ZnCl2 + ___ H2
11.00 moles of HCl and excess Zn will produce what mass, in grams, of ZnCl2?
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Chemistry – Stoichiometry Notes
Example 6 – Mass (g) A to Moles B
___ H2 + ___ O2  ___ H2O
2.39 g of H2O requires how many moles of H2?
___ Zn + ___ HCl  ___ ZnCl2 + ___ H2
How many moles of H2 will be produced from 13.41 g of Zn and excess HCl?
Example 7 – Particles A to Particles B
___ H2 + ___ O2  ___ H2O
How many molecules of O2 must combine with excess H2 to produce 5.43 x 1023 molecules of water?
___ Zn + ___ HCl  ___ ZnCl2 + ___ H2
How many formula units of ZnCl2 are produced when 1.32 x 1024 atoms of zinc react with excess HCl?
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Chemistry – Stoichiometry Notes
Example 8 – Mass (g) A to Mass (g) B
___ H2 + ___ O2  ___ H2O
What mass, in grams, of O2 is needed to react completely with 7.89 g of H2?
___ Zn + ___ HCl  ___ ZnCl2 + ___ H2
What mass, in grams, of H2 will be produced from 6.17 g of HCl and excess Zn?
Example 9 – Particles A to Mass (g) B
___ H2 + ___ O2  ___ H2O
7.08 x 1022 molecules of H2 and excess O2 will produce what mass, in grams, of H2O?
___ Zn + ___ HCl  ___ ZnCl2 + ___ H2
What mass, in grams, of Zn is needed to react completely with 8.63 x 1024 molecules of HCl?
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Chemistry – Stoichiometry Notes
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Example 10 – Mass (g) A to Particles B
___ H2 + ___ O2  ___ H2O
5.18 g of H2O requires how many molecules of H2?
___ Zn + ___ HCl  ___ ZnCl2 + ___ H2
How many atoms of Zn will react with excess HCl to produce 78.22 g of ZnCl2?
Percent Yield:
Example 11 – Percent Yield
Stoichiometry results in calculated, or _____________, amounts; percent yield tells us the percent of the
expected result that was actually produced.
Formula:
An experiment has an expected yield of 4.23 mol of AgNO3. Only 3.81 mol were actually collected. What is the
percent yield?
A combustion reaction produces 6.76 g of CO2, but it was calculated that 10.00 g would be produced. What is
the percent yield?