# Avogadro’s Number - PowerPoint PPT Presentation

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Avogadro’s Number. 6.02x10 23. mole = (mol) 602000000000000000000000. Mole. A mole is just a number like… Pair = 2Trio = 3 Dozen = 12Baker’s dozen = 13 Gross = 144Score= 20 Century=100Ream=500. How BIG is a mole?. There are ~ 6.6 billion people on Earth

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#### Presentation Transcript

6.02x1023

mole = (mol) 602000000000000000000000

### Mole

• A mole is just a number like…

Pair = 2Trio = 3

Dozen = 12Baker’s dozen = 13

Gross = 144Score= 20

Century=100Ream=500

### How BIG is a mole?

There are ~ 6.6 billion people on Earth

How many Earths would it take to equal the population

of 1 mole?

9.12 x 1013

• If you spent \$800 billion dollars a day how many years would it take to spend a MOLEion dollars?

2.06 x 109 years

• If you had a mole of cats . . .

They would create a sphere

larger than

Earth!

• If you had a mole of H2O could you swim in it?

NO! 

Water molecules are so small

that a mole of H2O = 18ml

• In chemistry we don’t work with individual atoms or molecules because they are too small to be weighed or measured

• We have to work with LOTS of atoms in order to measure them

THAT’s WHERE THE

MOLE COMES IN!

### How small are atoms?

• There are more atoms in one gram of salt than grains of sand on all the beaches

of all the oceans in all

the world.

of the

in

### Gram ATOMic Mass

• mass is in grams of 1 mole of atoms of an element

• In other words……

1 mol C atoms = 6.02 x 10 23 C atoms = 12g C

## Stoichiometry of Chemical Formulas

of the

in

### Gram Formula MassGram Molecular Mass Molar Mass

• mass in grams of 1 mole of a substance

• In other words . . . Add it all up!

1 mole of NaCl = 58g = 6.02x1023 particles of NaCl

1 mole of H2O = 18g = 6.02x1023 molecules of H20

### Now…..

• Use the gram formula mass and the gram atomic mass to determine

• how many moles or atoms of an element are found in some mass of a substance

• how much mass that element contributes to the mass of the entire substance

Use factor label & follow the units!

### Stoichiometry of Chemical Formulas

• If you have 1 molecule of (NH4)2SO4

• How many atoms of N are there?

• How many atoms of H?

SO…..

• If you have 1 mole of of (NH4)2SO4

• How many moles of N are there?

• How many moles of H?

PracticeRemember . . .1 mole = 6.02x1023atoms or molecules =______ gfm from the pt

Gases ONLY

@STP

### Molar Volume

• 1 mole of ANYgas

O2 (g)

NH3 (g)

He (g)

contains 6.02 x 1023 molecules and

occupies a volume of 22.4L

• STP

standardtemperature & pressure

0oC or 273K

101.3kPa or 1 atm

### Remember . . .

• Gases also have mass

1 mole of O2(g) = 32g

1 mole of NH3(g) = 17g

 we can calculate Density!

### D = m/v

• A sample of oxygen contains 3 moles of particles at STP what is its density?

• 2 steps

• Convert moles to mass AND volume

• Calculate density

• If mass or volume is given, use it and convert the other……. THEN calculate D!

Remember . . .

1 mole = 6.02x1023atoms or molecules =gfm = 22.4L (g)

“it’s a simple matter

of weight ratios . . .”

### Stoichiometry of Chemical Equations

• The study of quantitative relationships that can be derived from chemical equations.

• If you look at chemical equations as recipes it may be easier to understand that

• changing the amount of a reactant will change the amount of the product IN THE SAME RATIO!

### Examining Molar Relationships in Balanced Equations

6CO2 + 12 H2O + 2804kJ  6O2 + C6H12O6 +6H20

Balanced equations

• Law of conservation of mass / matter

• ATOMS are not createdor destroyed during a chemical reaction, they are only rearranged to form new substances.

• # atoms on reactant side = # atoms on product side

• Law of conservation of E

• E on the reactant side = E on the product side

Practice