The Mole Mass & The Mole

Ch. 10.1-10.2

CHM Hon.

How do you measure matter?

• Measure the amount by:– Counting– Mass– Volume

Measuring Matter

• Different forms of measurement relate– 1 dozen apples = 12 apples– 2.0 kg apples = 1 dozen apples– 1 dozen apples = 0.2 bushel apples

Finding Mass from a Count

• What is the mass of 9 average-sized apples if 1 dozen apples has the mass of 2.0 kg?

• 15 kg

Finding Mass from a Count

• If 0.20 bushel is 1 dozen apples and a dozen apples has a mass of 2.0 kg, what is the mass of 0.5 bushel of apples?

• 5.0 kg

What is a mole?• Remember: Matter is composed of atoms,

molecules and ions

• Mole (mol) – 6.02 x 1023 representative particles of that

substance – The SI Unit for measuring the amount of a

substance

What is a mole?

• Avogadro’s number– The number of representative particles in a

mole– 6.02 x 1023

– Avogadro (1776-1856): Italian scientist who helped clarify the difference between atoms and molecules

The Representative Particle• Refers to the species present in a substance

– Usually atoms, molecules or formula units– The representative particle of most elements is the

atom– Sometimes the representative particle is a molecule

ex) Molecular compounds (H2O)• 7 elements normally exist as diatomic molecules

– H2, N2, O2, F2, Cl2, Br2, I2

The Representative Particle

– A mole of any substance contains Avogadro’s number of representative particles (6.02 x 1023)

Converting Number of Particles to Moles

• 1 mol = 6.02 x 1023 representative particles

• Conversion Factor:

Converting Number of Particles to Moles

Converting Number of Particles to Moles

• 0.208 mol Mg

How many moles is 2.8 x 1024

atoms of silicon?

• 4.65 mol Si

Converting Moles to Number of Atoms

• 1.40 x 1025 atoms

amu

• Remember that atomic mass of an element (the mass of a single atom) is expressed in atomic mass units!– Relative values based on C-12 atom

• C-12 atom = Mass 12 amu• H atom = Mass 1 amu

Atomic mass & Molar mass

• Molar mass = the mass of a mole of an element• The Atomic mass of am element expressed in grams

is the mass of a mole of the element– Carbon: molar mass = 12 g– Hydrogen: molar mass = 1 g– Sulfur: molar mass = ?– Mercury: molar mass = ?

32.1 g

200.6 g

Molar mass is the mass of 1 mol of atoms of any element!!

Magnesium (Mg):

1 mol Mg 6.02 x 1023 atoms Mg Molar mass 24.3 g

Determining the Mass of a Mole of a Compound

• First step: determine the molecular formula– Ex) Sulfur trioxide:

• Second step: calculate the mass of the molecule– Add the atomic masses of the atoms

Finding the Molar Mass of a Compound

34.0 g

Finding the Molar Mass of a Compound

Find the molar mass of PCl3106.5 g

Mole to Mole conversion

13.1 mol Ca

Determine the number of moles in 25.5 g Ag

0.236 mol Ag

Mass to Atoms Conversion

How many atoms are in 55.2 g Li?

4.79 x 10 24 atoms Li

Atoms to mass Conversion

0.366 g He

What is the mass in grams of 6.02x1024 atoms Bi

2.09 x 103 g Bi

I am so confused!?

Putting it into prospective…

MASS MOLES REP. PARTICLES