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The Mole

The Mole. One mole = 6.023 x 10 23 quantity (Avogadro’s #) The representative particles are: Atoms: One mole of atoms = 6.02 x 10 23 atoms. Molecules: One mole of molecules = 6.02 x 10 23 molecules. Ions: One mole of ions = 6.02 x 10 23 ions

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The Mole

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  1. The Mole

  2. One mole = 6.023 x 1023 quantity (Avogadro’s #) The representative particles are: • Atoms: One mole of atoms = 6.02 x 1023 atoms. • Molecules: One mole of molecules = 6.02 x 1023 molecules. • Ions: One mole of ions = 6.02 x 1023 ions • Compounds: One mole of compound = 6.02 x 1023 compounds. The Mole: An expression of the quantity of matter. The quantity of matter is referred to a representative particles.

  3. Reference the periodic table. • 1 mole of Na atoms = 6.02 x 1023 Na atoms= 23g (the atomic mass of Na) • *the atomic mass of any element is the molar mass of that element. To determine:The mass in moles of an atom:

  4. PRACTICE • How many moles of water are found in 95.1 grams of water?

  5. How many atoms of water is that?

  6. PRACTICE How many moles of N2 would be in a 2.5 L container at STP?

  7. PERCENT COMPOSITION

  8. What is the percent of fat grams in a 
quarter pounder with cheese? What is 
the percent of sugar?

  9. Refers to what part by mass of a compound does each element contribute. • Formula: Mass of element X 100 = % Mass of compound Percent Composition

  10. Calcium Chloride : CaCl2 Ca: 1 x 40 = 40 Cl: 2 x 35 = 70 110 is the total mass • % Comp Ca = 40 x 100 = 36.36 % 110 • % Comp Cl = 70 x 100 = 63.6 % 110 100 % Sample

  11. EMPIRICAL FORMULAS

  12. Expression of the smallest whole number ratio of elements in a molecule. • May or may not be the same as the molecular formula. • Total percentage of any compound is 100%. Empirical Formula

  13. 1. Convert % to mass (total percentage is 100%). • 2. Convert mass to moles via the molar mass. • 3. Divide the moles by the smallest mole value to determine the mole ratio within the compound. • 4. If not a whole number, multiply the mole ratio from #3 by the smallest whole #. • 5. The answers are the subscript in the empirical formula. Empirical Formula

  14. MOLECULAR FORMULAS

  15. Actual number of elements expressed in a molecule. a. molecular formula = empirical formula x n b. Formula: molar mass of the molecule = n mass of the empirical formula n = the number of moles Molecular Formula

  16. Practice; Molecular formula

  17. HYDRATES

  18. Any salt that has water chemically bonded to the ions in the crystal structure is a hydrate or hydrated crystal. • Copper(II) sulfate is a hydrate. • Hydrated copper(II) sulfate is deep blue in color. What is a Hydrate?

  19. BaCl2•2H2O • FeSO4•6H2O • Na2CO3•10H2O • CuSO4•5H2O What does the Chemical Formula of A Hydrate Look Like?

  20. BaCl2•2H2O • barium chloride dihydrate • FeSO4•6H2O • iron(II) sulfate hexahydrate • Na2CO3•10H2O • sodium carbonate decahydrate • CuSO4•5H2O • copper(II) sulfate pentahydrate How are Names of Hydrates Written?

  21. What prefixes are used?

  22. Heat the crystal. The water is loosely bound, and will come away as water vapor. • Put the crystal in contact with or near a desiccant, maybe in a desiccator. How can the water be removed?

  23. What is the compound called after the water has been removed? • Anhydride (noun) • The light blue powder is the anhydride. • Anhydrous (adjective) • Anhydrous copper(II) sulfate is left in the test tube after heating.

  24. Compounds with water molecules attached. • a. Review the prefixes. P: 351 IN BOOK • b. The mass of the water is included in the mass of the total molecule. • c. Calculation of % composition, empirical formula and molecular formula is the same with hydrate. EXCEPT the mass of the water molecules are included. Hydrates

  25. A 15.67 g sample of a hydrate of magnesium carbonate was heated, without decomposing the carbonate, to drive off the water. The mass was reduced to 7.58 g. What is the formula of the hydrate? PRACTICE: HYDRATE FORMULA

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