Avogadro's Number (How we count atoms)

                                     
                    6.02 x 10²³

• atoms and molecules are extremely small 
• macroscopic objects contains too many to count or weigh individually 
• Amedeo Avogadro proposed that the number of atoms in 12.00000g of Carbon be equal to a constant (this is equal to 1 mole of Carbon)
• this value is now called Avogadro's number and forms the basis of all quantitative chemistry                         

• 10 mol = 6.02 x 10²³
• one mole is simply a multiple of things
• 1 pair = 2
• 1 dozen = 12
• 1 century = 100
• 1 mole = 6.02 x 10²³
• one mole rapresents a huge numbers of particles :

Particle
Atom	Element	(6.020 x 1023) / 1mole Fe (atoms)
Molecule	Covalent compounds	(6.02 x 1023) / 1mole CO2 (molecules)
Formula Unit	Ionic compound	(6.02 x 1023) / 1mole NaCl (formula units)

  

Example: A sample of Carbon contains 2.47 x 10²⁵ atoms. How many moles of 

              Carbon is this?

• 2.47 x 10²⁵ atoms x ( 1 mole / 6.02 x 10²³ atoms ) = 41 mol

Example: 12.5 moles of O2 rapresents how many molecules? 

• 12.5 mol x ( 6.02 x 10²³ molecules / 1 mole ) = 7.53 x 10²⁴ mol 

Example: How many Formula Units are present in 0.57 mol of BaCl2 ?

• 0.57 mol x (6.02 x 10²³ Formula Units / 1 mole ) = 3.4 x 10²³ Formula Units

-Eva