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2 SI unit for an amount 3 different pieces to this: Mass counting atoms---volume of a gas (later chap.) Mole is abbreviated mol (gee, that s a lot quicker to write, huh?)

3 The Mass of 1 mole (in grams) Use the Periodic table! Equal to the weighted average atomic mass 1 mole of C atoms = g 1 mole of Mg atoms = g 1 mole of Cu atoms = g

4 NaOH = FIRST decimal is a 0 or a 9 Na = g/mol O = g/mol H = g/mol Na = 23 g O = 16 g H = 1 g Sum = g/mol or simply grams JUST ADD ATOMS! Sum = 40 grams ROUNDING

5 EXAMPLE Cl 2 Each Cl = g Cl 2 is g In the world of the atom, this is quite different from = 70 g. The more atoms, the worse the error.

6 Nope! Molar masses are known quantities- do NOT effect SF Stop

7 find your given, arrange conversion factors evaluate your answer

8 Write the given top left Put the same unit of what you were given in the bottom right and the units of what you want to find in the top right. have units wanted units leaving

9 22 grams of copper is the given, Since grams of copper is the unit of what you were given, put this in the bottom right 22 g Cu g Cu

10 Since you want moles of copper put "moles of copper" as your unit in the top right. 22 g Cu mole Cu g Cu

11 Molar mass is the amount in ONE mole Note: the CF between grams and moles is just the mass of copper from the Periodic table. 22 g Cu 1.0 mole Cu g

12 Cancel units Multiply numerators and divide by any denominators For this: 22 divided by Your answer, 0.35 moles of copper (2 SF)

13 1) Where do you find molar mass? 2) How do you place a CF? 3) What determines SF? Could you do this for 22 g of CuO? What stays the same? What would change? Do you have questions?

14 PART 2

15 When used as a counting number, it is similar to a dozen, except it s a 602,200,000,000,000,000,000, X 10 23

16 FYI: This number is named in honor of Amedeo Avogadro ( ) He studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present id=868323&imagetype=thumb&height=125&widt h=155

17 Enough soft drink cans to cover the surface of the earth to a depth of _? over 200 miles. A mole of unpopped popcorn kernels spread across America: the country would be covered in popcorn to a depth of? over 9 miles. Count atoms at the rate of 10 million per second, it would take about? years to count the atoms in one mole 2 billion years.

18 FYI It was MEASURED in lab Now: we have even better ways of measuring using x-ray technology

19 1 mole of cookies = 1 mole of cars = X cookies X cars 1 mole of Al atoms = X atoms The NUMBER is always the same, but the MASS is very different The mass of a mole of cars is NOT the same as a mass of a mole of Al atoms

20 1 mole C = x C atoms 1 mole H 2 O = x H 2 O molecules 1 mole NaCl = x NaCl formula units FYI: I never dock points for calling an ionic compound a molecule

21 DO NOT USE particles as the unit! Put in the ACTUAL unit for the problem! (watch for this in homework) Use EITHER atom or molecule

22 6.022 x particles 1 mole or 1 mole 6.022x particles Reminder: a particle could be an atom OR a molecule!

23 1.50 moles of sodium is how many atoms? 1.50 moles Na x atom 1 mole Na Simply multiply; no SF since it s counting Use the given as a guide to be reasonable with your answers! 9.03 x atoms Na

24 For BOTH mass and particles it is ALWAYS ONE MOLE! To practice Avogadro try #1, 3, 5 remember answers are in back

25 Next we will pull the 2 concepts together Then to practice avogadro s number: Worksheet done in teams

26 6.02 X atoms or molecules= 1 mole AND 1 mole = molar mass (grams) You can convert atoms/molecules to moles and then moles to grams. (Two step process)

27 molar mass Avogadro s number Grams Moles atoms/molecules Everything must go through Moles!!!

28 You can t go directly from atoms to grams: You MUST go through MOLES. FYI: That s like asking: How many ounces would 2 dozen cookies weigh if 1 cookie weighs 4 oz? You have to convert from dozen first to an actual number

29 How many atoms of Cu are present in 35.4 g of Cu? 35.4 g Cu 1 mol Cu X atoms Cu g Cu 1 mol Cu = 3.35 X atoms Cu

30 Have you noticed? It is not just one unit- but the name of the chemical too.

31 How many molecules are present in 78.1 g of water? Lay out the set-up

32 How many molecules are present in 78.1 g of water? 78.1 g H 2 O 1 mol H 2 O X molecules 18 g H 2 O 1 mol H 2 O Answer: 2.61 x molecules H 2 O