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Moles and Equations
-Stoichiometry is
the study of the
quantitative
aspects of
chemical
reactions.
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Types of Chemical Reactions
1. Synthesis
2. Decomposition
3. Single Replacement
4. Double Replacement
5. Combustion
In order to communicate, scientists needed a
counting unit for very small particles such as: atoms,
molecules, ions
The mole
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LITERS
OF GAS
AT STP
Molar Volume
(22.4 L/mol)
MASS
IN
GRAMS
Molar Mass
(g/mol)
MOLES
6.02  1023
particles/mol
NUMBER
OF
PARTICLES
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Moles and Equations
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• The coefficient of a balanced chemical reaction
represents the number of moles of all
substances involved.
CH4 + 2O2 => CO2 + 2 H2O
Mole ratio:
Mass ratio:
1
:
2
:
1
:
2
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Let´s take a look at balancing a chemical
equation:
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2HI => H2 + I2
• a) How many moles of I2 are produced
when 450g of HI decomposes?
Steps:
1.
Write and balance the chemical equation:
H2 + I2 => HI
balancing
H2
+ I2
=> 2HI
2. Write the mole ratio:
1
:
1
: 2
3. Convert the mole ratio to mass ratio by multiplying the mole by the
molecular mass of the substance. ( n = m/MM)
2g
:
253.8g : 255.8g
4. Convert to molecule ratio by multiplying moles by avogadro´s number.
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• 4. Convert moles to molecule ratio by multiplying moles by
avogadro´s number.
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Write the mole and mass ratio for
the combustion of C3H6
We saw that:
• The coefficients in a balanced chemical equation
shows how many moles of one reactant are needed
to react with other reactants and how many moles
of product will be formed.
• Stoichiometry is the method by which we can
relate substances in a chemical reaction.
Stoichiometry is basically the same as a recipe for
cooking .
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• 1. How many moles of C3H6 are required to
produce 260g of water?
C3 H6 + O2 => CO2 + 6H2 O
• 2. How much carbon dioxide will be formed
when 500g of oxygen burns?
Given the combustion of ethanol, C2H5OH:
• 1. How much oxygen is required in order to
burn 700g of ethanol?
• 2. How much carbon dioxide is produced
when 6 moles of ethanol burns?
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Practice
•
Answer the following questions for the given reactions. Show your work!
Cl2(g) + NaI(aq)  NaCl(aq) + I2(s)
a) If you have 3 moles of chlorine, how many moles of sodium chloride do you
have?
b) If you have 31 g of iodine, how many moles of sodium iodide do you have?
c) If you have 200g of NaI, what mass of iodine do you produce?
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Online Quiz
• http://chem.lapeer.org/Chem1Docs/MolQuiz.html
Moles and Volume
• The conditions 0 0C and 1 atm are called standard
temperature and pressure (STP).
• Experiments show that at STP, 1 mole of a gas
occupies a volume of 22.4 L
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Mole Map
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1. Calculate the number of moles of ammonia
gas, NH3, in a volume of 80 L of the gas
measured at STP.
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• How many liters will 2.5 mol of H2 occupy at STP?
•
N2 is found to occupy 11.6L at STP. What is the mass
of the gas?
• At STP a sample of oxygen gas contains 11.5 mol. How
many L of oxygen are there?
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• What volume of hydrogen will react with 22.4 liters of
oxygen to form water? (All volumes are measured at STP)
Volume and Equations - Gas Stoichiometry
1. What is the volume of CO2 produced at STP when
5.60 g of glucose are used up in the reaction:
C6H12O6 (s) +
O2 (g)
=>
CO2 (g) +
H2O (l)
http://www.arps.org/users/hs/thompsom/collegeprep/unit_5/Gas_Stoichiometry_Worksheet.pdf
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2. When sulfur burns in air it forms sulfur
trioxide. What volume of this gas is
produced when 1 g of sulfur burns?