Honors Chemistry
Name: ________________________________________ Date: ______________ Mods: __________
Chapter 3.4 Notes: Avogadro’s Number, Moles, & Conversions
I. The Mole (abbreviated mol)
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A counting unit that chemists find extremely useful!
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Similar to counting by dozens … but chemists count by moles!
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Just like one dozen is always equal to 12, one mole is equal to Avogadro’s number
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1 mol = 6.022 x 1023 atoms/molecules/particles = Avogadro’s number
o
1 mole is the same value for any compound or atom regardless of its chemical identity
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1 mol of Zn = 6.022 x 1023 atoms Zn
1 mol of H2O = 6.022 x 1023 molecules H2O (molecular/covalent compound)
1 mol of CaCl2 = 6.022 x 1023 formula units CaCl2
1 mol of NO3– ions = 6.022 x 1023 NO3– ions
1 mol of electrons = 6.022 x 1023 e–
II. Molar Mass (abbreviated MM)
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While a dozen is always represented by the same number, 12 cows weigh significantly more
than 12 ducks …
o
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Similarly, while a mole of anything is equal to 6.022 x 1023, the mass of one mole
specifically depends on the identity of the substance being investigated
What is molar mass (MM)?
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The mass, in grams, of one mole of a given substance
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You calculate molar mass exactly the same way you would calculate formula weight,
only the units are different ( MM units = g/mol)
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Examples: MM of B = 10.8 g/mol (aka: 1 mol B = 10.8 g B)
MM of H2O = 18 g/mol (aka: 1 mol H2O = 18 g H2O)
MM of Mg(OH)2 = 58.3 g/mol (aka: 1 mol Mg(OH)2 = 58.3 g Mg(OH)2)
o
Molar Mass = # grams
# moles
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Practice: If 13.88 moles of an unidentified element has a mass of 556.59
grams, what element is it?
III. Conversions Using the Mole
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This requires the use of DIMENTIONAL ANALYSIS!
Using Molar Mass:
# grams
1 mol
Using Avogadro’s Number:
1 mol
6.022 x 10 atoms/molecules/particles
23
The Mole-Mass Map!!!
1) Gram  Mole
Find the number of moles in 1.1 grams of iron (III) chloride. Formula =___________________
2) Mole  Gram
Find the number of grams in 21.3 moles of barium carbonate. Formula =_________________
3) Mole  Atom or Molecule
Find the number of molecules in 3.2 moles of carbon tetrachloride. Formula =_____________
4) Atom or Molecule  Mole
Find the number of moles in 1.25x1023 molecules of nitrogen. Formula = _________________
5) Gram  Atom or Molecule
Find the number of molecules in 60 grams of lithium oxalate. Formula = _________________
6) Atom of Molecule  Gram
Find the number of grams in 3.24x1023 molecules of xenon hexafluoride. Formula = ________
7) Gram Compound  Atoms of Element ***
Find the number of carbon atoms in 17.8 grams of tricarbon octahydride. Formula = ________
8) Atoms of Element  Gram Compound ***
Find the mass of potassium chromate given 5.8x1021 atoms of potassium. Formula = _______
Gram  Mole Conversions
Given the following, find the number of moles:
1)
30 grams of hydrofluoric acid
2)
564 grams of copper
3)
89 grams of lead (IV) acetate
Mole  Gram Conversions
Given the following, find the number of grams:
4)
4 moles of copper (II) cyanide
5)
5.6 moles of tricarbon octahydride
6)
9.3 x 10-3 moles of silver
Mole  Atom or Molecule Conversions
Given the following, find the number of atoms or molecules:
7)
4 moles of silicon dioxide
8)
5.6 moles of mercury
9)
1.2 moles of beryllium iodate
Atom or Molecule  Mole Conversions
Given the following, find the number of moles:
10)
1.7x1023 molecules of phosphorous acid
11)
3.3x1022 atoms of arsenic
12)
4.5x1023 molecules of bromine
Gram  Atom or Molecule Conversions
Given the following, find the number of atoms or molecules:
13)
24 grams of iron (III) fluoride
14)
450 grams of sodium nitrite
15)
122 grams of selenium
Atom or Molecule  Gram Conversions
Given the following, find the number of grams:
16)
7.4 x 1023 molecules of silver nitrate
17)
4.5 x 1023 molecules of sulfuric acid
18)
9.4 x 1025 molecules of hydrogen
Mixed Review of Gram MoleAtom or Molecule Conversions
1)
How many grams are there in 3.3 x 1023 molecules of dinitrogen hexoxide?
2)
How many molecules are there in 4.23 moles of ammonium hydroxide?
3)
How many grams are there in 0.92 moles of boron trichloride?
4)
How many moles are there in 4.5 x 1022 molecules of barium nitrite?
5)
How many moles are there in 9.34 grams of lithium chloride?
6)
How many grams do 4.3 x 1021 molecules of uranium hexafluoride weigh?
7)
How many molecules are there in 230 grams of ammonium hydroxide?
8)
How many atoms of chlorine are there in 200 grams of carbon tetrachloride? ***
9)
What mass of zinc phosphite is present if there are 1.79 x1023 atoms of phosphorous? ***