Stoichiometry and the Math of Equations
Part 2: Mass-Volume
Objectives
• -Determine the molar relationships between reactants and products in a reaction equation
• -Use molar relationships and molar volume to convert between mass and volumes of components in a reaction
2
Equations
• Equations are quantitative-there is a mathematical relationship between reactants and products
a) mass-mass problems b) mass-volume problems c) volume-mass problems d) volume-volume problems•
3
Molar Volume
• Molar volume- the volume of 1 mole of ANY gas – Directly related to the number of gas
molecules – 1 mole of any gas contains the same
number of molecules (6.02 1023) so the volume of 1 mole of any gas is the same volume! 22.4 liters!
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Molar Volume• The volume of one mole is affected by
temperature and pressure changes– Assume we’re working under standard
conditions of temp and pressure, called STP, which is T =273 K (0° Celsius) and P =1 atm pressure
• Conversion factors: 22.4 liters OR 1 mole 1 mol 22.4 liters
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Molar Volume Problem #1• Mass – Volume• How many liters of hydrogen will
combine with 10.0 grams of oxygen to make water vapor?
• Steps(1) write and balance the equation (2) indicate the given and required (3) indicate the mole relationship
between the given and the required below the equation
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How many liters of hydrogen will combine with 10.0 grams of oxygen to
make water vapor?• Steps (1-3) ? L 10.0 g
2 H2 + O2 2 H2O
2 mole 1 mole? L H2 =• Step (4)10.0 g O2 x 1 mol O2 x 2 mol H2 x 22.4 L H2
1 32.0 g O2 1 mol O2 1 mol H2
= 14.0 L H2
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Molar Volume Problem #2
• Volume – Mass• How many grams of hydrogen will
combine with 15 liters of oxygen to make water vapor?
• Steps (1-3)
? g 15 L
2 H2 + O2 2 H2O
2 mole 1 mole8
How many grams of hydrogen will combine with 15 liters of oxygen to make
water vapor?
• Step (4)
? g H =
15L O2 x 1 mol O2 x 2 mol H2 x 2.02g H2 = 1 22.4 L O2 1 mol O2 1 mol H2
= 2.7 g H2
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Molar Volume Problem #3
• Volume-VolumeHow many liters of water vapor can be made if 5.0 liters of hydrogen combine with oxygen?Steps (1-3)
5.0L ? L2 H2 + O2 2 H2O
2 mole 2 mole10
How many liters of water vapor can be made if 5.0 liters of hydrogen combine
with oxygen?
• Step (4)
? L H2O =
5.0 L H2 x 1 mol H2 x 2 mol H2O x 22.4 L H2O
1 22.4 L H2 2 mol H2 1 mol H2O
= 5.0 L H2O11
Objectives
• -Determine the molar relationships between reactants and products in a reaction equation
• -Use molar relationships and molar volume to convert between mass and volumes of components in a reaction
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