Chapter 9 Notes I
Stoichiometry
Stoichiometry
Calculations of quantities in
chemical reactions
This means using balanced
equations to calculate quantities
of chemicals used in a chemical
reaction
A chemical equation is like a
recipe; it shows you how much
of each “ingredient” is used and
how much product you will have
in the end.
N2 + 3H2 a 2NH3
How many molecules of N2 are there?
How many molecules of H2 are there?
How many molecules of NH3 are there?
So one molecule of N2 will react with 3
molecules of H2 to form 2 molecules of
NH3.
You could also say that one mole of N2 will
react with 3 moles of H2 to form 2 moles of
NH3.
The heart of stoichiometry is
using a balanced chemical
equation as a conversion
factor for dimensional analysis.
Zn + HCl a ZnCl2 + H2
For the above reaction, how many moles
of zinc chloride can be produced with 0.27
moles of zinc?
Zn +2 HCl a ZnCl2 + H2
For the above reaction, how many moles
of zinc will react with 1.39 moles of
hydrochloric acid?
Why are mole/mole problems
impractical in a laboratory
setting?
4Fe + 3O2 a 2Fe2O3
How many grams of iron (III) oxide can be
produced with 17.2g Fe?
4Fe + 3O2 a 2Fe2O3
How many grams of iron will react with
5.25 liters of O2 (@STP)?
4Fe + 3O2 a 2Fe2O3
How many molecules of O2 are needed to
produce 3.92g Fe2O3?
Density
Remember, a conversion from liters to
moles is only valid for gases at STP.
Converting from/to liters (or mL) for liquids
or solids involve using density as a
conversion factor.
If you have 10.0mL of isopropyl
alcohol (C3H7OH) and burn it,
how many liters CO2 gas are
produced @STP? The reaction
is combustion.
D = 0.798g/mL
10.0mL (C3H7OH)
D = 0.798g/Ml
how many liters CO2
Find Mass using D=M/V
Write the reaction
2C3H7OH + 9O2 6CO2 + 8H20
7.98g
?L