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?