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Chapter 11

Chapter 11. The Mole. The Mole and Avogadro’s Number. The unique chemistry counting number is the mole. The associated counting number with the mole is Avogadro’s number, 6.02 x 10 23 particles. 1 mol = 6.02 x 10 23 particles Particles can be atoms, ions, formula units, or molecules.

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Chapter 11

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  1. Chapter 11 The Mole

  2. The Mole and Avogadro’s Number • The unique chemistry counting number is the mole. • The associated counting number with the mole is Avogadro’s number, 6.02 x 1023 particles. • 1 mol = 6.02 x 1023 particles • Particles can be atoms, ions, formula units, or molecules. • Example: Al is an atom. Mg2+ is an ion. Rb2O is a formula unit. CO2 is a molecule. • In you calculations you will not use the word particles. You will use one of the words listed above.

  3. Examples • mol particles • 2 mol H2  particles • 4.92 mol Al particles • particles  mol • 5.37 x 1018 ions of Ag+  mol

  4. Moles and Grams • What is the decimal number beneath every element on the periodic table? 1 atom Li 1 mol Li 6.941 amu 6.941gLi • Examples • 1 mol Ag = 107.868gAg • 1 mol Fe = 55.845gFe

  5. Why do Masses Vary? • The size of atoms vary • Example: If you have 50gCu and 50gAu which would contain the largest number of atoms? • Cu and has a mass of 63.546 amu • Au and has a mass of 196.967 amu • A mass of 50g will occupy the box. • Therefore, the smaller the atom the smaller the mass of one atom.

  6. Examples • 7.21 g Ni  mol Ni • 1.47 molSn  g Sn • You do: • 2.73 g Ca  molCa • 4.56 mol S  g S

  7. Grams to Particles • Two step • 2.15g Mg  atoms Mg • 2.973g Li  atoms Li • 7.92x1013 ions of Ag+  g Ag+ • Will electrons effect the mass of an element?

  8. Homework • Pg 346 89-106

  9. Conversions • g mol (1 mol/g) • mol  g (g/mol) • particles  mol (1 mol/6.02x1023 particles) • mol  particles(6.02x1023 particles/1mol) • particle  g 1 molX g 6.02x1023 particles 1 mol g  particles 1 mol X 6.02 x1023 particles g 1 mol

  10. Mole Relationships from a Chemical Formula • Determine the number of moles for Mg2+ and Cl- in 4.25 mol MgCl2. • What do you think you have? • 1 mol Mg2+ per 1 mol MgCl2 • 2 molCl- per 1 mol MgCl2 • AgNO3(aq) + MgCl2(aq)  • If I wanted this to happen: • Everything occurs in certain ratios • I can figure out moles of Mg2+ and Cl- from MgCl2 • Can I determine the correct amount of grams?

  11. Example • Determine the amount of moles for P and O in 3.15 mol of P2O5.

  12. Molar Mass • Determine the molar mass of P2O5. • Molar mass of P: 30.97gP / 1 mol P • Molar mass of O: 15.99gO / 1 mol O • Molar mass of P2O5 • 2(30.97gP) + 5(15.99gO) / 1 mol P2O5 • You do: • Determine the molar mass of Fe2(SO4)3

  13. Examples • 2.91 mol Fe2(SO4)3 g • 129 g CO2  mol • 53.2 g NaCl  mol, particles, and ions of Cl-

  14. Homework • Pg 347 • 107-121 do b and d • Above 121 do odd problems

  15. Percent Composition • % of each element involved in a chemical cpd. • Example: CaCl2

  16. Empirical Formula • The simplest whole number ratio of atoms in a chemical compound. It may or may not be the molecular formula. • Example: • Molecular formula: H2O2 • Empirical formula: HO

  17. Example • A substance is found to contain 36.84% N and 63.16% O. What is the empirical formula? • Use four digits calculating moles • When getting to whole number ratio, you can round very little. • Example • 0.993 can be rounded to 1 • 0.745 cannot be rounded • Decimal numbers must become a whole number

  18. Example • You do: Pg. 333 # 49

  19. Molecular Formula • The actual whole number ratio of a chemical compound. It is a multiple of the empirical formula. • MF = n(emp F) • MM (molar mass) = n(emp mass) • n = MM / emp mass • Always find the empirical formula first.

  20. Example • Pg 335 #51 • You do #52

  21. Formula for a Hydrate • Ahydrate is an ionic compound with an attached water molecule. • The water of hydration is attached to the surface of the cpd. • An anhydrate is a compound with no water attached. • How to name • CuSO4. 5H20 • Copper (II) sulfate pentahydrate

  22. Example • Pg. 340 63 • MgSO4 . xH2O • You must detemine x and name the hydrate • x = mol H2O / mol anhydrate • You do #64

  23. Homework • Pg. 139 #139, 144, 145, 153

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