Empirical Formulas and Molar Mass:

Part 2-Mass, Atoms, Moles

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Objectives

• -Be able to use atomic mass to relate grams, moles and atom number

• -Determine the number of atoms, moles, and grams of different substances

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Mass, Atoms, Moles

• KC4H5O6 is the empirical formula for cream of tartar

• How many atoms of oxygen are in 1 formula unit of cream of tartar?

6 atoms O

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Mass, Atoms, Moles

• KC4H5O6

• How many atoms are in 1 formula unit of cream of tartar?

16 atoms

1 potassium4 carbon5 hydrogen6 oxygen

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Mass, Atoms, Moles

• KC4H5O6 • How many formula units are in 1

mole of cream of tartar? 6.02 x 1023 formula units

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Mass, Atoms, Moles

• KC4H5O6 • How many atoms of oxygen are in

(PER) 1 mole of cream of tartar?• ? atoms O/mole KC4H5O6 =

6 atoms O x 6.02 x1023 formula unit KC4H5O6 1 formula unit KC4H5O6 1 mole KC4H5O6

=3.61 x 1024 atoms O/mole KC4H5O6 6

Mass, Atoms, Moles

• KC4H5O6

• How many moles of oxygen atoms are in 1 mole of cream of tartar?

• Let’s put this in perspective……….

7

How many wheels are in a dozen bicycles?

1 bicycle = 2 wheels1 dozen bicycles = 2 dozen wheels

1 mole bicycles = 2 mole wheels8

How many dozen hydrogen atoms are in 1 dozen water molecules?

1 water = 2 hydrogen1 dozen water = 2 dozen hydrogen1 mole water = 2 mole hydrogen

H2O9

Mass, Atoms, Moles

• So………• KC4H5O6 • How many moles of oxygen atoms

are in 1 mole of cream of tartar?

6 moles O

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Mass, Atoms, Moles

• KC4H5O6 • What is the mass of the oxygen

atoms in (PER) 1 mole of cream of tartar?

? g O/ mole KC4H5O6

16.0 g O x 6 moles O x = 96.0 g O1 mole O 1 mole KC4H5O6 mole

KC4H5O6 11

Let’s Do It!!!

• How many atoms in one formula unit?

Magnesium Acetate: Mg(C2H3O2)2

1-Mg4-C6-H4-O

15 total atoms12

Let’s Do It!!!

• How many formula units in one mole of

Magnesium Acetate: Mg(C2H3O2)2

6.02 x 1023 formula units

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Let’s Do It!!!!

• How many oxygen atoms are in one formula unit?

Magnesium Acetate: Mg(C2H3O2)2

4 oxygen atoms

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Let’s Do It!!!• How many oxygen atoms are in one

mole of this substance?

Magnesium Acetate: Mg(C2H3O2)2

? O atoms = mole Mg(C2H3O2)2

(4 O atoms) x (6.02 x 1023 units Mg(C2H3O2)2 ) =

unit Mg(C2H3O2)2 mole Mg(C2H3O2)2

= 2.41 x 1024 atoms O mole Mg(C2H3O2)2

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Let’s Do It!!!

• How many moles of oxygen atoms are in one mole of this

substance?Magnesium Acetate:

Mg(C2H3O2)2

4 moles of Oxygen16

Let’s Do It!!!• What is the mass of oxygen atoms

in one mole of this substance? Magnesium Acetate: Mg(C2H3O2)2

? g O =1 mole Mg(C2H3O2)2

16.0 g O x 4 moles O 1 mole O 1 mole Mg(C2H3O2)2

= 64.0 g O/ 1 mole Mg(C2H3O2)2

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Objectives

• -Be able to use atomic mass to relate grams, moles and atom number

• -Determine the number of atoms, moles, and grams of different substances

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