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The Mole Is BackChemistry 10
Mole Gangnam Stylehttps://www.youtube.com/watch?v=HnRHBw-xjVo
Lesson Essential Question
How do I convert moles to mass, formula units,
atoms, ions and molecules?
Mole Map
Grams
mole
molecules
atoms
Atoms (eleme
nt)
6.02 x 1023
6.02 x 1023
# atoms per
molecule
6.02 x
1023
formula
unit
# ions per formula
unit
Mr
Dimensional AnalysisHow many moles are in 45.7 g
of NO2?
Molar mass NO2 = 14.007 g + 2(15.999 g) = 46.005 g/mol
1. Ask yourself the question – Can I convert directly from grams to moles?
YES – molar mass has units of grams/mole
2. Start with your “given” from the original problem.
3. Use conversion factor that will allow you to “cancel” out grams and give you moles.
45.7 g of NO2
46.005 g
1 mol
= 0.993 mol
4. Calculate & express answer with correct sig. figs. and units!
Dimensional Analysis
1. Ask yourself the question – Can I convert directly from moles to atoms of an element?YES – there are 6.02 x 1023 atoms per mole
2. Start with your “given” from the original problem.3. Use conversion factor that will allow you to “cancel” out grams and give you moles.
10.0 mol Fe
1 mol Fe
6.02 x 1023 atoms Fe= 6.02 x 1024 Fe atoms
4. Calculate & express answer with correct sig. figs. and units!
How many atoms are in 10.0 moles of Iron (Fe)?
Dimensional Analysis
1. Ask yourself the question – Can I convert directly from grams to molecules?
NO– I have to go through moles
2. Start with your “given” from the original problem.3. Use conversion factor that will allow you to “cancel” out grams and give you moles.
12.1 g H2SO4
98.078 g
1 mol
= 7.37 x 1022 molecules
4. Calculate & express answer with correct sig. figs. and units!
How many molecules are in 12.1 g of H2SO4?
6.02 x 1023 molecules
1 mol
Dimensional Analysis
NOTE: How many atoms are in 1 molecule of H2SO4?
210.0 g H2SO4
98.078 g
1 mol
= 9.023 x 1024 atoms
How many atoms are in 210.0 g of H2SO4?
6.02 x 1023 molecules
1 mol
2H + 1S + 4O = 7 total atoms per molecule
1 molecule H2SO4
7 atoms
Dimensional Analysis
What is the formula for potassium oxide?
32.6 g K2O
94.195 g
1 mol
= 2.08 x 1023 formula units
How many formula units are in 32.6 grams of potassium oxide?
6.02 x 1023 f. units
1 mol
K2O
Dimensional Analysis
What is the formula for lithium sulfate?
125 g Li2SO4
109.944 g
1 mol
= 1.37 x 1024 Li ions
How many lithium ions are in 125g of lithium sulfate?
6.02 x 1023 f. units
1 mol
Li2SO4
1 f. unit Li2SO4
2 Li ions
How many lithium ions are in one formula unit?
2
