2. The Mole

4. Molar Mass 0 Also called atomic mass, formula mass, molecular mass 0 Unit = g/mol 0 Calculating Molar Mass 0 Use the average atomic mass from the periodic table 0 For atoms = atomic mass Ex. C = 12.011 g/mol Fe = 55.847 g/mol 0 For compounds = sum of the atomic masses of the atoms that are in the formula 0 EX: CaI 2 = 40.078 g/mol + 2 (126.904) g/mol = 293.886 g/mol 0 EX: (NH 4 ) 3 PO 4 = 3(14.007) + 12(1.0079) + 30.974 + 4(15.999) = 149.086 g/mol

5. The Mole 0 How do you measure how much you have? 0 Counting (impractical – too many particles) 0 Weighing 0 Volume 0 Particles cannot be counted directly, but we need to know how many particles are there. 0 In chemistry we use the mole to figure out how many particles there are when we weigh something or measure the volume of something. 0 Mole = the SI unit for how much of a substance or amount 0 The mole is a unit similar to dozen- just many more than 12 0 It tells you how many you have.

6. The Mole 1 dozen = 1 gross = 1 ream = 1 mole = 12 144 500 6.02 x 10 23 There are exactly 12 grams of carbon-12 in one mole of carbon-12.

7. 0 Particles  moles or moles  particles Use Avogadro’s Number = 1 mole = 6.02 X10 23 particles (atoms, molecules, formula units) *FOR ANY SUBSTANCE 0 Grams  moles or moles  grams Use the molar mass from the periodic table. 0 Liter  moles or moles  liter For Gases at STP (standard temperature and pressure) 1 mole = 22.4 L

8. Avogadro’s Number 6.02 x 10 23 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro (1776-1855). Amadeo Avogadro I didn’t discover it. Its just named after me!

9. Calculating Formula Mass Calculate the formula mass of carbon dioxide, CO 2. 12.01 g + 2(16.00 g) = 44.01 g  One mole of CO 2 (6.02 x 10 23 molecules) has a mass of 44.01 grams

10. Avogadro’s Number 0 602,214,000,000,000,000,000,000 0 Avogadro’s # of sheets of paper stacked one sheet on top of another would reach beyond our solar system. 0 Avogadro’s # of basketballs could create a new planet the size of Earth. 0 Avogadro’s # of grains of rice would cover the land masses of the Earth to a depth to 75 meters. 0 Avogadro’s # of pennies. You decided to give away $1 million dollars a day to every person on Earth, it would take more than 3000 years to distribute all of your money

11. Mole Relationships Mole Atoms or molecules Atoms or molecules Liters Grams 6.02 x 10 23 AtomicMassAtomicMass 22. 4 L

12. Molar Mass Avogadro’s Number 22.4 L/mol Particles Atoms Molecules f.u. MoleMass (g) Volume (L)

13. Particles atoms, molecules, or formula units Mass Volume (Gas at STP) Molar Mass 22.4 Avogadro’ s Number Mole Conversions

14. Calculations with Moles: Converting moles to grams How many grams of lithium are in 3.50 moles of lithium? 3.50 mol Li = g Li 1 mol Li 6.94 g Li 24.3

15. Calculations with Moles: Converting grams to moles How many moles of lithium are in 18.2 grams of lithium? 18.2 g Li = mol Li 6.94 g Li 1 mol Li 2.62

16. Calculations with Moles: Using Avogadro’s Number How many atoms of lithium are in 3.50 moles of lithium? 3.50 mol = atoms 1 mol 6.02 x 10 23 atoms 2.07 x 10 24

17. Calculations with Moles: Using Avogadro’s Number How many atoms of lithium are in 18.2 g of lithium? 18.2 g Li = atoms Li 1 mol Li 6.022 x 10 23 atoms Li 1.58 x 10 24 6.94 g Li1 mol Li (18.2)(6.022 x 10 23 )/6.94

18. 0 Ex. How many moles are in 8.04*10 24 atoms Fe? 0 ? g = 8 mol Al 2 (SO 4 ) 3

19. Calculations with Moles: Using Standard Molar Volume How many moles of hydrogen are in 100 L of hydrogen at STP? 100 L = mol 22.4 L 1 mol 4.64

20. Calculations with Moles: Using Standard Molar Volume How many liters are occupied by 3 moles of oxygen gas at STP? 3 mol = L 1 mol 22.4 L 67.2

21. 0 How many atoms are in 20.04 g Sn? 0 How many liters are equal to 8 moles of CO 2 ? 0 How many moles are equal to 2.4 L of O 2 ? 0 How many grams of O 2 are in 2.4 L O 2 ?

22. Atom & Mole Ratios *Within a formula, subscripts can be considered as the: 0 # of atoms within molecules of the compound 0 the # of moles of that element within moles of the compound. (Since avogadro’s # cancels out) Example: H 2 O Example: Ba 3 (PO 4 ) 2

23. Using Chemical Formulas: A raindrop contains about 0.050g of H 2 O. 0 How many molecules of water? 0 How many atoms of O within the water? 0 How many atoms of H?

25. % Composition 0 Percent Composition = The % by mass of each element in a compound. 0 Mass of part X 100 = % composition Total Mass Example: Find the % composition of Al 2 (SO 4 ) 3 *If you had 25.0 grams of this substance, How much would be Al?

26. Ex: Na 2 CO 3  10H 2 O. Find the % of water in this hydrate. EX: Find the % composition of a compound containing tin and chlorine if 18.35 g of the compound contains 5.74 g of tin.

27. Molecular/Empirical Formula 0 Empirical Formula = smallest whole number ratio of moles of the elements in a compound 0 Molecular Formula = actual number and kinds of atoms present in a compound 0 Ex. Molec Formula = N 10 O 5 Emp Formula = N 2 O

28. Calculating Empirical Formula An empirical formula is a ratio of moles of each atom in a compound. 1. Must have the moles of each atom. *If you are given %, assume that you have 100 grams of the substance. Since % is out of 100, the % of each atom will equal grams of each atom. Convert grams to moles. 2. To find the lowest whole number ratio (mole ratio). Divide each # of moles by the smallest # of moles. 3. If a # in the ratio is.5 (.4 -.6), double everything. 4. Apply ratio to atoms given as subscripts. Ex. 25.9 g N & 74.1 g O

29. 25.9 g N & 74.1 g O

30. Calculating Molecular Formula 1. Calculate the empirical formula mass (efm) 2. Divide a given molar mass (molecular mass) by efm 0 Gives you the number of emp. form. in your molecular formula 3. Multiply the emp. form. by that # Ex. EF = CH 4 N Molar Mass = 60 g/mol

31. EX: EF = NO 2 Molar Mass = 138 g/mol Ex. 27.59 %C, 1.15 %H, 16.09 %N, 55.17 %O Molar mass = 261.1 g/mol. Find molecular formula