190 likes | 379 Views
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……………….
E N D
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 = 6.022 x 1023 particles particles is whatever: atoms, molecules,etc Avogadro’s number
The Mole • Conversion factor 1 mole 6.022 x 1023 particles 6.022 x 1023 particles 1 mole
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 6.022 x 1023 atoms Zn 1 mole Zn = 1.51 x 1024 atoms
Mole Problems 1) How many molecules of sucrose in 3.5 moles of sucrose? 3.5 mole sucrose 6.022 x 1023 molecules sucrose 1 mole sucrose = 2.11 x 1024 molecules
Mole Problems • Calculate the number of moles in 5.75 x 1024 atoms of aluminum. 5.75 x 1024 atoms Al 1 mole Al 6.022 x 1023 atoms Al = 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 14.0 g N 1 mol 14.01 8 16.0 g O 1 mol 15.99
Example Problems 1) What is the mass of 3.57 moles Al? mol g 13 3.57 mol Al 27.0 g Al Al = 96.3 g Al 1 mol Al 27.0 Molar mass Al
Example Problems 2) Calculate the mass of 4 moles of oxygen. mol g 8 4 mol O 16.0 g O O = 64 g O 1 mol O 15.99 Molar mass O
Example Problems 3) How many moles in 43.5 g sulfur? g mol 16 S 32.06 43.5 g S 1 mol S = 1.36 mol S 32.1 g S Molar mass S
Example Problems 3) How many moles in 28.5 g nitrogen? g mol 7 N 14.01 28.5 g N 1 mol N = 2.04 mol N 14.0 g N Molar mass N
Putting it all together Avogadro’s number Molar Mass particles grams moles