December 12, 2014
Stoichiometry
The quantitative relationships between
amounts of reactants used and products
formed by a chemical reaction.
December 12, 2014
Stoichiometry and the balanced chemical
equation.
Coefficients in a chemical reaction can represent
• Representative particles
• Moles of particles
H2O(l)
O2(g) + H2(g)
(*Balance this equation.)
Using stoichiometry, we can answer questions such as:
How many grams of oxygen is created by the
decomposition of 1 gram of water?
How many molecules of water are needed to create 10g
of hydrogen to be used in a fuel cell?
December 12, 2014
Mole Ratio
• Ratio between the numbers of moles of any two
substances in a chemical equation
• Used as conversion factors in stoichiometric
calculations
4Fe(s) + 3O2(g)
2Fe2O3(s)
Mole ratio relating iron and oxygen:
December 12, 2014
Mole Ratio
• Ratio between the numbers of moles of any two
substances in a chemical equation
• Used as conversion factors in stoichiometric
calculations
4Fe(s) + 3O2(g)
2Fe2O3(s)
Mole ratio relating iron and iron oxide:
December 12, 2014
Example 1:
**Complete and balance equation first
NaBr + Ca(OH)2
1. How many moles of NaOH are produced from 1.5
moles of NaBr?
2. How many moles of NaBr reacts with 2 moles of Ca
(OH)2?
December 12, 2014
December 12, 2014
Remember mole calculations? You can do the same
to complete a series of stoichiometric conversions.
•
•
•
•
•
mole-to-mole
mole-to-mass
mass-to-mass
mass-to-particles
...etc.
*Flip your notes over to the back,
and get a copy of the example
problems from Ms. K
December 12, 2014
Known (given)
Unknown
mass (g)
mass (g)
molar mass (periodic table)
molar mass (periodic table)
mole ratio
Moles
Avogardro's # = 6.022x1023
Particles
Moles
Avogardro's # = 6.022x1023
Particles
December 12, 2014
Known (given)
Unknown
molar mass (periodic table)
molar mass (periodic table)
mole ratio
Avogardro's # = 6.022x1023
Avogardro's # = 6.022x1023
December 12, 2014
Example 2: mole-to-mole
If 10.0 mol of propane (C3H8) is burned, how many
moles of carbon dioxide are formed?
C3H8 + 5O2
3CO2 + 4H2O
mass (g)
mass (g)
Moles
Particles
Moles
Particles
December 12, 2014
Example 3: Mass to mole problem
Mg(s) + HCl(aq)
*Balance equation first
MgCl2(aq) + H2(g)
If you start with .35g of magnesium ribbon, how many
moles of hydrogen gas is produced?
mass (g)
mass (g)
Moles
Particles
Moles
Particles
December 12, 2014
Example 4: Mole-to-mass
Cl2(g) +
Na(s)
NaCl
How many grams of table salt (NaCl) are produced from
1.25 moles of chlorine gas?
mass (g)
mass (g)
Moles
Particles
Moles
Particles
December 12, 2014
Example 5: Mass-to-mass
MgCO3
MgO + CO2
How many grams of carbon dioxide are produced from
11.0 grams of MgCO3?
mass (g)
mass (g)
Moles
Particles
Moles
Particles
December 12, 2014