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Published byHollie Singleton Modified over 8 years ago

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Topic: Counting Atoms and Formula Mass (the MOLE) Do Now: complete package page 2 Here is an example NaCl = 1 Na atom, 1 Cl atom H 2 SO 4 = 2 H atoms, 1 S atom, 4 O atoms

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Lets starting my counting atoms in a single molecule NaCl H 2 SO 4 Cu(NO 3 ) 2 What happens if there is a coefficient in the front? = More then 1 molecule Na = 1 Cl = 1 total atoms = 2 H = 2 S = 1 O = 4 total atoms = 7 5NaCl – 5 molecules of NaCl 2Cu(NO 3 ) 2 Na = 5 Cl = 5 total atoms = 10 Cu = 1 N = 2 O = 6 total atoms = 9 Cu = 2 N = 4 O = 12 total atoms = 18

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We can count the number of atoms in one molecule of water (H 2 0). 2 Hydrogens 1 Oxygen But in a 100 ml of water, how many H atoms / O atoms are there? Thousands, Millions, Billions? THINK BIGGER MUCH BIGGER MOLE VIDEO LINK

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Thanks to Avogadro, we can calculate that there are … 6,680,000,000,000,000,000,000,000 (6.68 x 10 24 ) Hydrogen atoms in 100 ml (less then a ½ cup) of water

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1 Mole = 6.02 x 10 23 particles = Avogadro’s # Used to “count” numbers of atoms Defined as # of atoms in 12 g of C-12 – This is the standard – So, 12 g of C-12 has ____________ atoms This is a really big number – It ’ s so big because atoms are really small! – HOW SMALL?! (link) HOW SMALL?! 6.02 x 10 23 No, not this kind of mole!

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One mole of water = 6.02 X 10 23 water molecules One mole of gorillas = 6.02 X 10 23 gorillas One mole of He atoms = 6.02 X 10 23 He atoms One mole of anything = 6.02 X 10 23 of that thing

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Equalities 1 mole of C-12 = 12.0 grams of C-12 = 6.02 X 10 23 atoms of C-12 0.5 mole of C-12 = 6.0 grams of C-12 = 3.01 X 10 23 atoms of C-12

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Remember how to find Atomic Mass? 9.0122 amu = 9 amu

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Formula mass (Gram Formula Mass –GFM) take atomic mass of any element and replace amu with grams – 9.0122 amu = 9.0122 g So, in 9 g of Be there are 6.02 X 10 23 atoms or 1 mole

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– Molar mass = formula mass per mol (g/mol) Chemists use this to convert between the number of atoms to an actual mass that they can measure in the lab 1 mole of H weighs 1 mole of C weighs 1 mole of U weighs 1.0079 g 12.011g 238.029g 6.02 x 10 23 H atoms 6.02 x 10 23 C atoms 6.02 x 10 23 U atoms 1.0079 g/mol 12.011 g/mol 238.029 g/mol

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Calculating Formula Mass (GFM) 1.COUNT Atoms 2.LOOK UP Atomic Mass ( and round) 3.Multiply by number of atoms 4. Add CH 2 Cl 2 – C = 1 – H = 2 – Cl = 2 X 12 = 12 X 1 = 2 X 35 = 70 84 g Molar Mass = 84 g/mol

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