Introducing…Introducing…

Hellooo

Students!!!

Mr. MOLEMr. MOLE

Chemistry Joke

Q: What did the proton say to the electron to make him happy?

A: Something positive!

What is a MOLE?What is a MOLE?

• Abbreviated “mol”• The amount of a substance that contains

6.02 x 1023 representative particles.• 6.02 x 1023 is called AVOGADRO’S NUMBER.• It is an equivalency—a conversion factor• Just like…1 dozen = 12 pieces, • 1 mole = 6.02 x 1023 pieces

Why 6.02 x 10Why 6.02 x 102323??????• Because atoms are so small, Avogadro’s

number has to be pretty big. How big?

–Scientists use this number because…• It is the number of particles in 12 It is the number of particles in 12 grams of carbon-12 grams of carbon-12

–602,000,000,000,000,000,000,000

If you had a mole of water molecules, how much water do you think this would be?

1 mole of water molecules (6.02 x 1023 molecules of water) is only about 18 mL of water !!

1 MOLE of Atoms

Using Moles in Chemistry

Definition – the amount of a substance that contains 6.02 x 1023 representative particles.

WWhat is a representative particle?• It is whatever you are counting:

– Molecules– Formula units– Atoms– Ions

• Our representative particle in this question is a molecule—it is what we are counting.

• We can use dimensional analysis: 1 mol CO2 = 6.02 x 1023 molecules CO2

A Typical Question:A Typical Question: How many molecules of CO2 are there in 4.56 moles of CO2 ?

4.56 mol CO2

1 mol CO2

6.02 x 1023 molecules CO2

(4.56) 6.02 x 1023 molecules CO2= 2.75 x 1024 molecules CO2

Moving On…Moving On…• Now that we can find how many

representative particles are in a given number of moles, and…

• How many moles are represented by a given number of representative particles,

• We need to learn about the mass of a mole.

The MOLAR MASS!!

Measuring the Mass of MolesMeasuring the Mass of Moles• Remember atomic mass?• The amu (atomic mass unit) is one

twelfth the mass of a carbon-12 atom.• Since the mole is the number of atoms in

12 grams of carbon-12…•The decimal number on the periodic The decimal number on the periodic table (average atomic mass) is ALSO the table (average atomic mass) is ALSO the mass of 1 mole of those atoms in grams.mass of 1 mole of those atoms in grams.

Finding the Molar Mass of Elements

Using the periodic table, what is the molar mass of…

Aluminum

Lead

26.98 g/mol

207.20 g/mol

Notice, we’re still talking about 1 mole. Each mole has the same number of particles (6.02 x 1023), just different masses!

amu grams / mole

26.98 g Al = 1 mol Al

207.20 g Pb = 1 mol Pb

Finding the Molar Mass of a Compound

H2O2 H = 2 x 1.01 = 2.02 g/mol

1 oxygen = 1 x 16.00 = 16.00 g/mol

2.02 g + 16.00 g = 18.02 g/mol

molar mass of water = 18.02 g/mol

It’s simple: Just add up its atomic masses. Example: What is the molar mass of water?

Calculate These Molar Masses:

Mg3(PO4)2 262.84 g/mol

C12H22O11 342.34 g/mol

• Molar massMolar mass is the generic term for the mass of one mole of any substance

• Also called: Gram Molecular Mass (molecules)Gram Formula Mass (ionic cmpds)Gram Atomic Mass (elements)

Practice Problem Using Molar MassPractice Problem Using Molar Mass

How many grams are in 0.25 mol of NaCl?1. Find the molar mass. (This will be the conversion factor.)

Na: 23.00 g/mol; Cl: 35.45 g/mol; NaCl: 23.00 + 35.45 = 58.45 g/mol

2. Use dimensional analysis to solve.

58.45 g NaCl = 1 mol NaCl

1 mol NaCl

0.25 mol NaCl 58.45 g NaCl =15 g NaCl

Another Practice Problem• How many moles are in 25 g of NaCl?1. Find the molar mass.

(This will be the conversion factor.)

Na: 23.00 g/mol; Cl: 35.45 g/molNaCl: 23.00 + 35.45 = 58.45 g/mol

2. Use dimensional analysis to solve. 1 mol NaCl = 58.45 g NaCl

58.45 g NaCl

25 g NaCl 1 mol NaCl =0.43 mol NaCl

ChemistryJoke

Q: What kind of music does a chemist listen to?

A: Heavy Metal!