THE MOLE

you know that certain quantities can be represented by various terms: dozen = pair = these terms make counting easier 12 2

Chemists need method for counting atoms in a sample Why? So there is a term for counting atoms or molecules……………….. Because atoms are small and there is an extremely large number to count

The Mole Defn – SI unit for measuring amount of substances What is the value of mole? 1 mole = x particles particles is whatever: atoms, molecules,etc Avogadro’s number

The Mole Conversion factor 1 mole x particles

The Mole 1 mole is a HUGE FREAKIN’ NUMBER!!!! The distance from earth to sun is 93 million miles. 1 mole of stacked paper can make that trip more than one million times!!

Mole Problems 1) How many atoms of zinc in 2.50 moles of zinc? 2.50 mole Zn mole Zn atoms Zn x = 1.51 x atoms

Mole Problems 1) How many molecules of sucrose in 3.5 moles of sucrose? 3.5 mole sucrose mole sucrose molecules sucrose x = 2.11 x molecules

Mole Problems Calculate the number of moles in 5.75 x atoms of aluminum x atoms Al atoms Al mole Al x = 9.55 mole Al

Question 1 dozen eggs 1 dozen doughnuts 1 dozen cokes 1 dozen cars 1 dozen computers 1 dozen elephants 1 dozen shoes Do all these have the same mass?

Question 1 mole copper 1 mole silver 1 mole hydrogen 1 mole gold 1 mole uranium 1 mole lead 1 mole iron Do all these have the same mass?

Why does 1 mole of different substances have different masses? 1) different size 2) different composition Mass of 1 mole Fe ≠ mass of 1 mole Cu

Molar Mass Defn – mass, in grams, of one mole of a substance Unit: g mol

Molar Mass What is the molar mass of nitrogen? What is the molar mass of oxygen? 7 N g 1 mol 8 O g 1 mol

Example Problems 1) What is the mass of 3.57 moles Al? mol  g 3.57 mol Al mol Al g Al Molar mass Al = 96.3 g Al 13 Al 27.0

Example Problems 2) Calculate the mass of 4 moles of oxygen. mol  g 4 mol O 1 mol O 16.0 g O Molar mass O = 64 g O 8 O 15.99

Example Problems 3) How many moles in 43.5 g sulfur? 43.5 g S g  mol mol S g S Molar mass S = 1.36 mol S 16 S 32.06

Example Problems 3) How many moles in 28.5 g nitrogen? 28.5 g N g  mol mol N g N Molar mass N = 2.04 mol N 7 N 14.01

Putting it all together moles particlesgrams Avogadro’s number Molar Mass