If you buy 2 cookies – you bought a ______ of cookies! If you buy 12 eggs – you bought a _________________! If you buy 144 pencils – You bought a _____________ of pencils! (Eeeeeeewwwww!!) If you buy 500 sheets of paper – You bought a _____________ of paper If you bought 1,000,000,000 bytes of memory on a USB drive – You bought a ______ of memory. If you bought 6.02 x10 23 chocolate chips, you bought a __________ of chocolate chips! Dozen, Gross, Ream, Gig are all just words used to describe a number!

Is another word for a specific number of items, (6.02 x10 23 things) a very large number of items! It’s useful for “counting” very large numbers of very small particles (atoms and molecules) Ie. Counting the grains of sand on a small beach!!

- they are impossible to count or weigh individually. 1. Therefore, to make the task of counting and weighing atoms easier, a very large quantity called a MOLE is used.

Therefore, a mole of tin cans would contain 6.022×10 23 tin cans. 1. This large number is called Avogadro’s Number. He was born in 1776 to a noble family of Italy. Avogadro is hailed as a founder of the atomic- molecular theory

1. So g of Na, is 1 mole of Na or 6.022×10 23 atoms of Na. 2. How many grams would 1 mole of Iron weigh? 55.8 g

The molar mass is the mass of 1 mole of particles - so… The molar mass of Carbon is 12.01g/mol The molar mass of Iron is 55.8 g/mol The molar mass of Sulphur is 32.1 g/mol

Molar Mass= sum of the atomic masses = 2 H’s + 1 O = 2(1.01) =18.02g/mol

- the same number of atoms as in 1 mole of any other element 1. 1 mole of He contains the same number of atoms as 1 mole of Au or Ag or Pb (OR ANY OTHER ELEMENT!). 2. Think elements’ atoms as fruit. Do 10 apples weigh the same amount as 10 watermelons? 3. Same thing with the elements ( 10 Hydrogen atoms are a very different size and weight than 10 Gold atoms – and therefore – the molar masses are different.

So… using the elements’ atomic masses 4.00g of He contains the same number of atoms as g of Au or g of Ag. (each helium atom weighs a lot less than a gold atom which is why the same number of each have a very different mass) The molar mass of Sulphur is 32.1 g/mol The molar mass of Mercury is 200.6g/mol

1. 1 mole of nickel (Ni) has a Molar mass of _______________ grams/ mole is the molar mass of 1 mole of _______ mole of Au contains the same number of atoms as 20.18g of ________ g of Cu contains ______ mole of Cu, which has the same number of atoms as ______ mole of Mo and both contain ______ atoms g of V contains _____ atoms of V which equals ______ of V g(atomic mass of Ni) Phosphorus (P) Neon (Ne) One (1) 6.022× 23 One (1) mole

If I were to add another mole of iron to this, How many moles of Iron would I have? What has happened to the atoms of Iron? How many more atoms would I have? What would happen to the mass? These are directly proportional to each other!!

1 mol of Iron = 6.02 x Atoms = 6.02x10 23 x moles So… in 3 moles of Iron… Atoms = 3 mols x 6.02 x atoms 1 mol = x atoms of Iron

1. Recall: 1 mole of nickel (Ni) has a mass of _______________. 2. Also: grams/ mole is the mass of 1 mole of _______ mole of water (H 2 O) has a mass of mole of C 6 H 12 O 6 has a molar mass of 58.96g (atomic mass of Ni) Phosphorus (P) g (it contains 1 oxygen, which weighs 16.00g and 2 hydrogen, which weigh 1.00g) =6(12.01)+12(1.00) +6(16.00) = g/mol

Mols = mass__ Molar Mass Molar Mass of N 2 = 14 x2 = 28g n = 50gN 2 or 50.0g x 1 mol =28.0g Moles = 1.79 There are 1.79 mols of N 2 in 50.0g of N 2

1) Try the Gram Formula Mass Worksheet 2) Try the Moles and Mass Worksheet (both sides)