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Lecture 10.1- The Mole

We often measure the amount of something by count, by mass, or by volume.

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In chemical reactions, atoms, molecules & salts react in specific ratios.

A chemist must be able to count molecules in order to run a reaction without having any leftover reactants.

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Atoms and molecules are very small.We need a very large number of atoms in order for a sample to be seen and worked with in a lab.The mole is a very big number!

The mole is the SI unit used to measure quantity.

A mole is 6.02 x 1023 particles602 000 000 000 000 000 000 000

6.02 x 1023 is Avogadro’s number

A mole is 6.02 x 1023 representative particles

Representative particles

The representative particle for covalent compounds is the molecule.

For most elements the r.p. is the atom,

but for diatomic elements it is the molecule

H2 N2 O2 F2 Cl2 Br2 I2

For salts it is the formula unit.

The official definition of one mole is the number of atoms in 12 grams of carbon-12.

The mole is a very big number!

• A mole of inches is 1,616,434 light years, or across our galaxy and back 8 times!

• 6.02 X 1023  Donut Holes: Would cover the earth and be 5 miles (8 km) deep.

• 6.02 X 1023  Pennies: Would make at least 7 stacks that would reach the moon.

• 6.02 X 1023  Grains of Sand: Would be more than all of the sand on Miami Beach.

• 6.02 X 1023  Blood Cells: Would be more than the total number of blood cells found in every human on earth.

• 1 Liter bottle of Water contains 55.5 moles H2O

• 5 Pound Bag of Sugar contains 6.6 moles of C12H22O11

Converting moles to number of particles

How many atoms are in 3.5 moles of Cu?

3.5 moles Cu

6.02x1023 atoms 1 mole Cu

X = 2.1 x 1024 atoms

6.02 x 3.5 ≈ 21 21 x 1023 = 2.1 x 1024

Converting number of particles to moles

We have 3.0 x 1025 molecules of water.

How many moles?3.0 x 1025 molecules

X _____1 mole______ 6.02 x 1023 molecules

≈ 50 moles of water

0.5 x 10(25-23) = 0.5 x 102

= 5 x 101

6.02 1023

3.0 x 1025

6.02 x 1023

≈ 50 moles of water

3.0 x 1025

Find out how Avogadro’s number is based on the relationship between the amu and the gram.

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The atomic mass is the mass of a single atom of a specific element (with units of amu).

The mass of one mole of a specific element (measured in grams) is known as its molar mass.The numerical value of both are equal, only the units change.

One atom of calcium has an atomic mass of 40.078amu.

One mole of calcium has a molar mass of 40.078g.

Lead 207.2amu per atom

207.2g per mole

Using the mole allows us to “count” the number of particles in a sample by mass.

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The molar mass of each element is given on the periodic table.

The Mass of a Mole of an Element

The Mass of a Mole of an Element

•One molar mass of carbon, sulfur, mercury, and iron are shown.

To calculate the molar mass of a compound, add the masses of the elements in the compound.

The Mass of a Mole of a Compound

• Substitute the unit grams for atomic mass units. Thus 1 mol of SO3 has a mass of 80.1 g.

SO3 contains 1 S and 3 O 1 x 32.1(mass of S) = 32.1 g 3 x 16.0(mass of O) = 48.0g

32.1 + 48 = 80.1g/mol of SO3

• Molar Masses of Glucose, Water, and Paradichlorobenzene

The Mass of a Mole of a Compound

1 mole is 6.02 x 1023 of anything

10.4

Molar Mass

Element- molar mass is on periodic table

Compound- Add the mass for each element in the compound.