Masses and moles
Not that kind of mole
Re-mem-memRe-mem-mem-member…
K19
39.0983
Potassium
Average atomic mass, in amu/atom
Re-mem-memRe-mem-mem-member…
K19
39.0983
Potassium
Assume the most common isotope has 39 p+n (19p and 20n)—but there are some heavier ones.
And now, for something completely different.
• Def:
1 mole=6.02 x 1023 particles
Not that kind of mole
As a conversion factor• 2.7 moles Ar = _?_atoms Ar
• 1.5 x 1021 molecules H2O=__?__moles H2O
.
As a conversion factor• 2.7 moles Ar = _?_atoms Ar
2.7 moles Ar x 6.02 x 1023 atoms Ar =
1 mole Ar
• 1.5 x 1021 molecules H2O=__?__moles H2O
1.5 x 1021 molecules H2O x 1mole H2O =
6.02 x 1023molecules H2O
As a conversion factor• 2.7 moles Ar = _?_atoms Ar
2.7 moles Ar x 6.02 x 1023 atoms Ar =
1 mole Ar
• 1.5 x 1021 molecules H2O=__?__moles H2O
1.5 x 1021 molecules H2O x 1mole H2O =
6.02 x 1023molecules H2O
1.6 x 1024 atoms Ar
.0025 moles H20
6.02 x 1023
6.02 x 1023
• Avogadro’s number.
• Amadeo Avogadro.
• He suggested that there is a number.
• The number is larger than he expected.
The greatest conversion of all time!
1 amu X 6.02 x 1023 = 1 gram
atom X 6.02 x 1023 mole
Avogadro’s number!
• Avogadro’s number is also the conversion from amu’s to grams.
• Both sets of units define the mole.
What is the mass?
• .0582 mol Ni
• 12.0 mol Ne
• 4.80 x 10 25 atoms Xe
• 1.24 x 10 21 atoms Au
What is the mass?
• .0582 mol Ni
• 12.0 mol Ne
• 4.80 x 10 25 atoms Xe
• 1.24 x 10 21 atoms Au
Convert to moles
first!
What is the mass?
• .0582 mol Ni
3.42 g Ni
• 12.0 mol Ne
242 g Ne
• 4.80 x 10 25 atoms Xe
10500 g Xe
• 1.24 x 10 21 atoms Au
.406 g Au
What is the mass?
• 2.4 mol He
• 9.03 x 10 23 atoms K
How many moles?
• 18.3 g Sr
• 4.8 g Ar
• 4.03 x 10 23 formula units of iron (III) oxide
• 7.24 x 10 21 molecules sulfur hexaflouride
How many moles?
• 18.3 g Sr
.209 mol Sr
• 4.8 g Ar
.12 mol Ar
• 4.03 x 10 23 formula units of iron (III) oxide
.669 mol Fe2O3
• 7.24 x 10 21 molecules sulfur hexaflouride
.012 mol SF6
How many moles?
• .130 g Ag
• 1.42 x 10 24 molecules nitrogen trichloride
Pop quiz
• If 1 mole of hydrogen atoms (H) has a mass of 1.0078 g, what is the mass of 1 mole of hydrogen molecules (H2)?
Pop quiz
• If 1 mole of hydrogen atoms (H) has a mass of 1.0078 g, what is the mass of 1 mole of hydrogen molecules (H2)?
• I hope you answered “Twice that mass.”, or 2.0156 g
Formula masses
• If I give you a formula, you add the masses of the atoms represented to get the formula mass.
• The units are grams/mole
What is the formula mass of…
• LiCl
• BaF2
• K2SO3
• Fe2(Cr2O7)3
• Na2HPO4 • 7H2O
What is the formula mass of…
• Gold (I) fluoride
• Lithium oxide
• Cobalt (II) cyanide
• dinitrogen trisulfide
• tetraphosphorus hexoxide
PS
• The subscripts in a formula can be read:
K2SO3
There are two potassium atoms in a formula unit
of potassium sulfite
There are two moles of potassium
in a mole of potassium sulfite
or
PS
• The standard molar volume for a gas is:
at STP
22.4L/mol
22.4L/mol
STP =standard temperature and pressure
= 273k, 1.00 atm
PS
is about22.4 L
Mole conversions
Mole conversions
Mass Moles
Mole conversions
Mass Moles
Use the formula mass
Mole conversions
Mass Moles
FM in grams = 1 mole
Mole conversions
Particles Moles
Mole conversions
Moles
Use Avogadro’s number
Particles
Mole conversions
Moles
6.02 x 10 23 particles = 1 mole
Particles
Mole conversions
MolesVolume of a gas at STP
Mole conversions
Moles
Use the molar volume
Volume of a gas at STP
Mole conversions
Moles
22.4 L gas at STP = 1 mole
Volume of a gas at STP
Mole conversions
Moles
Volume of a gas at STP
Particles
Mass
Use the formula mass
Use Avogadro’s
number
Use the molar volume
Styrene: an organic molecule, C8H8
1. What is the molecular weight of styrene?2. What is the empirical formula of styrene? 3. How much does 1.000 mole of styrene
weigh? 4. How much does 1.54 pmole of styrene
weigh? 5. How much many moles in 9.67 kg of
styrene? 6. How many moles in 84.6 mg of styrene?
Styrene: an organic molecule, C8H8
1. What is the mass % of C in styrene?
2. What is the mass % of H in styrene?
3. An unknown material is recovered from the Delaware River. Results from analysis of it are Carbon 92.26% Hydrogen7.74% Is it styrene?
4. The molecular weight of this compound is 78.11 grams per mole. What is its molecular formula?