1. CHEMISTRY 161 Chapter 4 The Mole

2. Macroscopic versus Microscopic Worlds 2 H 2 + O 2 2 H 2 O 1 liter water contains about 3.3 X 10 25 molecules

3. CHEMICAL MASS SCALE standard / calibration atomic mass unit (amu, u) one atom of carbon-12 12 u (exactly) we have to correlate u with kg

4. H2OH2O O: 15.999 u H: 1.008 u H 2 O: 18.015 u PSE formula mass: weight of one molecule

5. CaO O: 15.999 u Ca: 40.08 u CaO: 56.08 u formula mass: weight of one molecule correlation between u and kg

6. MOLE

7. one mole of a compound contains the same number of molecules/atoms as the number of atoms in exactly 12 g of 12 C Avogadro’s number N a 6.023 x 10 23

8. 1 mole of H 2 O 6.023 x 10 23 1 mole of 12 C 6.023 x 10 23 1 mole of NaCl 1 mole of Na 6.023 x 10 23 Avogadro’s number links micro and macroscopic world molecules atoms

9. 1 mole of H 2 O 6.023 x 10 23 molecules 1 molecule of H 2 O – 2 H atoms and 1 O atom 1 mole of H 2 O – 2 mole H atoms and 1 mole O atoms 6.023 x 10 23 molecules of H 2 O 6.023 x 10 23 atoms of O 2 x 6.023 x 10 23 atoms of H

10. H2OH2O O: 15.999 u H: 1.008 u H 2 O: 18.015 u 1 mole of H 2 O – 18.015 g 15.999 g/mol 1.008 g/mol NaNa NaNa NaNa

11. CaO O: 15.999 u Ca: 40.08 u CaO: 56.08 u 1 mole of CaO – 56.08 g

12. 1 mole of H 2 O – 18.015 g 6.023 x 10 23 molecules of H 2 O – 18.015 g one molecule of H 2 O – 2.99 x 10 -23 g molecular weight of one mole of H 2 O 18.015 g mol -1

13. 2 H 2 + O 2 2 H 2 O 2 molecules 1 molecule 2 molecules 2 moles 1 mole 2 moles 4.03176g 31.9988g 36.03g STOICHIOMETRY x g y g 70.0g

14. 2 H 2 + O 2 2 H 2 O 2 molecules 1 molecule 2 molecules 2 moles 1 mole 2 moles 4.03176g 31.9988g 36.03g STOICHIOMETRY x g y g 70.0g

15. Example I: How many grams of iron are in a 15.0 g sample of iron(III) oxide? 1. molecular formula 3. weight of one mole Fe 2 O 3 2. weight of one molecule Fe 2 O 3 159.7 u 159.7 g 4. 1 molecule Fe 2 O 3 contains 2 atoms of Fe 5. 1 mole Fe 2 O 3 contains 2 moles of Fe 159.7 g111.69 g 15.0 g x g x = 10.5 g

16. Example II: How many grams of oxygen are in a 10.0 g sample of nickel (II) nitrate? 1. molecular formula 3. weight of one mole Ni(NO 3 ) 2 2. weight of one molecule 4. 1 molecule Ni(NO 3 ) 2 contains 6 atoms of O 5. 1 mole Ni(NO 3 ) 2 contains 6 moles of O x = 5.25 g

17. Example III: How many atoms are in 10 kg of sodium? 1 mole sodium = 22.98977 g 6.023 x 10 23 atoms = 22.98977 g x atoms = 10,000 g x = 2.6 x 10 26 atoms

18. Example IV How heavy are 1 million gold atoms? 1 mole gold = 196.96654 g 6.023 x 10 23 atoms = 196.96654 g 1,000,000 atoms = x g x = 3.2 x 10 -16 g = 0.32 fg

19. Mass Percentage Composition P 4 O 10 =X 100 % =

20. Example V A sample was analyzed and contains 0.1417 g of nitrogen and 0.4045 g of oxygen. Calculate the percentage composition. 1. mass of whole sample 2. percentages of elements =X 100 %

21. EMPIRICAL FORMULA H2OH2O H2O2H2O2 MOLECULAR FORMULA HO H2OH2OH2OH2O P 4 O 10 P2O5P2O5 P 2*2 O 2*5

22. Example A sample contains 0.522 g of nitrogen and 1.490 g of oxygen. Calculate its empirical formula. N2O5N2O5

23. COMBUSTION CxHyCxHy CO 2 H2OH2O

24. COMBUSTION C3H8C3H8 CO 2 + H 2 O 0.013068 g + O 2 How many grams of oxygen are consumed? 1.balance equation 2.convert to moles

25. The combustion of a 5.217 g sample of a compound of C, H, and O gave 7.406 g CO 2 and 4.512 g of H 2 O. Calculate the empirical formula of the compound. How many grams of Al 2 O 3 are produced when 41.5 g Al react? 2Al(s) + Fe 2 O 3 (s) Al 2 O 3 (s) + 2 Fe(s)

26. LIMITING REACTANT C 2 H 4 + H 2 O C 2 H 5 OH

27. excess reactant limiting reactant

28. How many grams of NO can form when 30.0 g NH 3 and 40.0 g O 2 react according to 4 NH 3 + 5 O 2 4 NO + 6 H 2 O 2 C 2 H 2 + 5 O 2 4 CO 2 + 2 H 2 O

29. THE YIELD 2 C 2 H 2 + 5 O 2 4 CO 2 + 2 H 2 O theoretical yield of CO2: 10 g actual yield of CO2: 8 g = X 100 %