Other Stoichiometric Calculations
Objective
I
can calculate
stoichiometric quantities
from balanced chemical
equations using units of
volumes for gasses at STP.
Other Stoichiometric Calculations


As you know…..
Moles can then be expressed 3 ways:
1.
2.
3.



units of mass – (using the molar mass)
numbers of particles – (using Avogadro's number = 6.02X1023)
volume of gas – (using 22.4L at STP)
So……You can always convert the Given quantity to moles
Then use the mole ratio from the balanced equation to
calculate the moles of the Unknown
Then convert the moles of the Unknown substance into any
other unit of measurement.
Other Stoichiometric Calculations


As you know…..
A balanced chemical equation indicates the relative number of
moles of reactants and products.
aG
(Given quantity)

bU
(Unknown quantity)
b mol U
mol G 
 mol U
a mol G
Other Stoichiometric Calculations

Mole to Mole Example:
N2 (g) + 3 H2 (g) 
2 NH3 (g)
Given 0.50 mol of hydrogen, how many moles of ammonia will be
produced?
Note: “…how many moles…” = The “Unknown” is moles of NH3
2 mol NH3
0.50 mol H 2 
 0.33 mol NH3
3 mol H 2
Other Stoichiometric Calculations



As you also know…..
A balanced chemical equation indicates the relative number of
moles of reactants and products.
If the Given and Unknown quantity is a mass of substance, you
use the molar mass to convert to moles
aG

bU
(Given quantity)
(Unknown quantity)
1 mol G
b mol U mass of U
mass of G 


 mass of U
mass of G a mol G
1 mol U
Other Stoichiometric Calculations

gram to gram (mass to mass) Example:
N2 (g) + 3 H2 (g)  2 NH3 (g)
Given 1.0 g of hydrogen, how many grams of ammonia will be
produced?
Note: “…how many grams…” = The “Unknown” is grams of NH3
1 mol H 2 2 mol NH3 17.0 g NH3
1.0 g H 2 


 5.7 g NH3
2.0 g H 2
3 mol H 2
1 mol NH3
Stoichiometry with Gasses



A balanced chemical equation indicates the relative number of
moles of reactants and products.
But in chemistry problems, the Given and Unknown quantity
could be a gas which is measured in liters (L) of volume at STP.
For gas volume at STP, simply use 22.4L to convert to moles
aG

bU
(Given quantity)
(Unknown quantity)
1 mol G
b mol U 22.4 L of U
Volume of G 


 Volume of U
22.4 L of G a mol G
1 mol U
Stoichiometry with Gasses

liter to liter (volume to volume) Example:
N2 (g) + 3 H2 (g)  2 NH3 (g)
Given 11.2 liters of hydrogen, what volume (in liters) of ammonia
will be produced?
Note: “…what volume…” = The “Unknown” is liters (L) of NH3
1 mol H 2 2 mol NH3 22.4 L NH3
11.2 L H 2 


 7.5 L NH3
22.4 L H 2 3 mol H 2
1 mol NH3
Stoichiometry with Gasses

liter to liter (volume to volume)

You try it!!
___ SO2 (g) + ___ O2 (g)  ___ SO3 (g)
Given 9.90 liters of oxygen gas, what volume (in liters) of
sulfur trioxide gas will be produced?
_______________ x ________________ x ____________ x _______________
Stoichiometry with Gasses

liter to liter (volume to volume)

You try it!!
2 SO2 (g) + 1 O2 (g) 
2 SO3 (g)
Given 9.90 liters of oxygen, what volume (in liters) of
sulfur trioxide will be produced?
1 mol O 2 2 mol SO3 22.4 L SO3
9.90 L O 2 


 19.8 L SO3
22.4 L O 2 1 mol O 2
1 mol SO 3
Other Stoichiometric Calculations


As you know…..
Moles can then be expressed 3 ways:
1.
2.
3.



units of mass – (using the molar mass)
numbers of particles – (using Avogadro's number = 6.02X1023)
volume of gas – (using 22.4L at STP)
So……You can always convert the Given quantity to moles
Then use the mole ratio from the balanced equation to
calculate the moles of the Unknown
Then convert the moles of the Unknown substance into any
other unit of measurement.
Objective
I
can calculate
stoichiometric quantities
from balanced chemical
equations using units of
volumes for gasses at STP.