Stoichiometry
Math behind Chemistry
Review
• Student knows how to
calculate molar mass of
a compound.
• Find the molar mass of
dinitrogen tetraoxide.
• Student knows how to
convert from grams to
moles and moles to
grams using molar
mass.
• Example: How many
moles are in 12.56
grams of NaCl?
Mole to Mole
• Mole Ratios
• A ratio between compounds that comes from
the coefficients of balanced equation of a
chemical equation.
• Written 3 ways:
• Fraction 3/2
• Words 3 to 2
• Colon 3:2
Mole Ratios
• Must come from balanced chemical equation,
whether equation is given to you to balance or
word equations.
• Example: When Calcium iodide combines with
Sodium oxide, calcium oxide and sodium iodide
are formed. Write the chemical formulas and
balance it.
•1CaI2 + 1Na2O 1CaO + 2NaI
Mole Ratios cont
•1CaI2 + 1Na2O 1CaO + 2NaI
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Identify all the ratios that can be made possible.
1 to 1
1 to 1
1:2
1:1
½
1 to 2
Mole to Mole Conversion
• Once you have balanced equation, you convert
from moles of one compound to moles of a
different compound.
• Let’s use the previous example to solve a
problem.
• 1CaI2 + 1Na2O 1CaO + 2NaI
• How many moles would form of CaO if an
experiment started with 6.74 moles of Na2O?
Example 1
•1CaI2 + 1Na2O 1CaO + 2NaI
• How many moles would form of
CaO if an experiment started
with 6.74 moles of Na2O?
6.74 moles Na2O x
Mole ratio
from
balanced
equation
1 𝑚𝑜𝑙𝑒 𝑜𝑓 𝐶𝑎𝑂
1 𝑚𝑜𝑙𝑒 𝑜𝑓Na2O
=6.74 moles CaO
Example 2
•1CaI2 + 1Na2O 1CaO + 2NaI
•How many moles of CaI2
are needed if 5.32 moles of
NaI are formed?
Example 3
• Write the balanced equation:
•Aluminum bromide and Chlorine
react to form aluminum chloride
and bromine.
1.
How many moles of bromine are formed if an
experiment starts with 4.61 moles aluminum
bromide?
2. How many moles of chlorine are needed to
form 7.88 moles of bromine?
Recap
•Students know how to:
A. Calculate molar mass
B. Convert mass to moles
C. Convert moles of known
compound to moles of unknown
compound using mole ratios
Learning Check
Potassium metal and chlorine gas combine to
potassium chloride.
1. Calculate the molar mass of chlorine
2. Convert 5.87 grams of chlorine to moles of
chlorine.
3. Using the moles of chlorine from step 2, how
many moles of potassium chloride will form?