Transcript Chapter 6
Chapter 6
Chemical Quantities
1
How you measure how much?
You can measure mass,
or volume,
or you can count pieces.
We measure mass in grams.
We measure volume in liters.
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We count pieces in MOLES.
Moles
Defined as the number of carbon
atoms in exactly 12 grams of carbon12.
1 mole is 6.02 x 1023 particles.
Treat it like a very large dozen
6.02 x 1023 is called Avogadro’s
number.
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Representative particles
The smallest pieces of a substance.
For a molecular compound it is a
molecule.
For an ionic compound it is a formula
unit.
For an element it is an atom.
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Types of questions
How many oxygen atoms in the
following?
– CaCO3
– Al2(SO4)3
How many ions in the following?
– CaCl2
– NaOH
– Al2(SO4)3
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Types of questions
How many molecules of CO2 are the in
4.56 moles of CO2 ?
How many moles of water is 5.87 x 1022
molecules?
How many atoms of carbon are there in
1.23 moles of C6H12O6 ?
How many moles is 7.78 x 1024 formula
units of MgCl2?
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Measuring Moles
Remember relative atomic mass?
The amu was one twelfth the mass
of a carbon 12 atom.
Since the mole is the number of
atoms in 12 grams of carbon-12,
the decimal number on the periodic
table is also the mass of 1 mole of
those atoms in grams.
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Gram Atomic Mass
The mass of 1 mole of an element in
grams.
12.01 grams of carbon has the same
number of pieces as 1.008 grams of
hydrogen and 55.85 grams of iron.
We can write this as
12.01 g C = 1 mole
We can count things by weighing
them.
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Examples
How much would 2.34 moles of
carbon weigh?
How many moles of magnesium in
24.31 g of Mg?
How many atoms of lithium in 1.00 g
of Li?
How much would 3.45 x 1022 atoms
of U weigh?
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What about compounds?
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in 1 mole of H2O molecules there are two
moles of H atoms and 1 mole of O atoms
To find the mass of one mole of a
compound
– determine the moles of the elements
they have
– Find out how much they would weigh
– add them up
What about compounds?
What is the mass of one mole of CH4?
1 mole of C = 12.01 g
4 mole of H x 1.01 g = 4.04g
1 mole CH4 = 12.01 + 4.04 = 16.05g
The molecular mass of CH4 is 16.05g
The mass of one mole of a molecular
compound.
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Gram Formula Mass
The mass of one mole of a compound.
Calculated the same way.
What is the GFM of Fe2O3?
2 moles of Fe x 55.85 g = 111.70 g
3 moles of O x 16.00 g = 48.00 g
The GFM = 111.70 g + 48.00 g = 159.70g
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Molar Mass
The generic term for the mass of one
mole.
The same as molecular mass, gram
formula mass, and gram atomic
mass.
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Examples
Calculate the molar mass of the
following and tell me what type it is.
Na2S
N2O4
C
Ca(NO3)2
C6H12O6
(NH4)3PO4
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Using Molar Mass
Finding moles of compounds
Counting pieces by weighing
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Molar Mass
The number of grams of 1 mole of
atoms, ions, or molecules.
We can make conversion factors
from these.
To change grams of a compound to
moles of a compound.
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For example
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How many moles is 5.69 g of NaOH?
For example
How many moles is 5.69 g of NaOH?
5.69 g
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For example
How many moles is 5.69 g of NaOH?
mole
5.69 g
g
need to change grams to moles
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For example
How many moles is 5.69 g of NaOH?
mole
5.69 g
g
need to change grams to moles
for NaOH
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For example
How many moles is 5.69 g of NaOH?
mole
5.69 g
g
need to change grams to moles
for NaOH
1mole Na = 22.99g 1 mol O = 16.00 g
1 mole of H = 1.01 g
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For example
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How many moles is 5.69 g of NaOH?
mole
5.69 g
g
need to change grams to moles
for NaOH
1mole Na = 22.99g 1 mol O = 16.00 g
1 mole of H = 1.01 g
1 mole NaOH = 40.00 g
For example
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How many moles is 5.69 g of NaOH?
1 mole
5.69 g
40.00 g
need to change grams to moles
for NaOH
1mole Na = 22.99g 1 mol O = 16.00 g
1 mole of H = 1.01 g
1 mole NaOH = 40.00 g
For example
How many moles is 5.69 g of NaOH?
5.69 g
need to change grams to moles
for NaOH
1mole Na = 22.99g 1 mol O = 16.00 g
1 mole of H = 1.01 g
1 mole NaOH = 40.00 g
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1 mole
= 0.142 mol NaOH
40.00 g
Examples
How many moles is 4.56 g of CO2 ?
How many grams is 9.87 moles of
H2O?
How many molecules in 6.8 g of
CH4?
49 molecules of C6H12O6 weighs how
much?
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