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Mass, the Mole, and Avogadro’s Number

Mass, the Mole, and Avogadro’s Number. (Molar Mass). The Mass of a Mole C-12 Basis. Atomic masses are based on the mass of a C-12 atom. Molar masses are based on the mass of a mole of C-12 atoms. Molar Mass (MM). Definition The mass in grams of 1 mole of any substance.

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Mass, the Mole, and Avogadro’s Number

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  1. Mass, the Mole, and Avogadro’s Number (Molar Mass)

  2. The Mass of a MoleC-12 Basis • Atomic masses are based on the mass of a C-12atom. • Molar masses are based on the mass of a mole of C-12 atoms.

  3. Molar Mass(MM) • Definition • The mass in grams of 1 mole of any substance. • Has the units g / mol • Units

  4. Molar Mass of Elements • The molar mass (MM) of any element is numerically equal to its atomic mass. 20 Ca40.08 Ex: Molar mass of Ca Ex: Molar mass of Cl 17Cl35.45

  5. Molar Mass of Compounds • The molar mass (MM) of a compound is determined the same way, except now you add up all the atomic masses for the molecule (or compound) 20 Ca40.08 • Ex: Molar mass of CaCl2 • Avg. Atomic mass of Calcium = 40.08g • Avg. Atomic mass of Chlorine = 35.45g 17Cl35.45 • Molar Mass of calcium chloride =40.08 g/mol Ca + (2 X 35.45) g/mol Cl110.98 g/mol CaCl2

  6. Molar MassPractice Problem • Calculate the Molar Mass of calcium phosphate • Formula = • Masses of elements: • Molar Mass = • = Ca3(PO4)2 Ca = 40.078 g P = 30.974 g O = 15.999 g 3 (40.078 g) + 2 (30.974 g) + 8 (15.999 g) 310.174 g Ca3(PO4)2 / mole

  7. Molar MassPractice Problems • Find the molar mass of: • Copper • Sulfuric acid • Xenon tetrafluoride • Hypochlorous acid • Oxygen 63.55 g / mol 98.06 g / mol 206.9 g / mol 52.45 g / mol 31.99 g / mol

  8. Flowchart Representative Particles 1 mol______ 6.02 X 1023 particles 6.02 X 1023 particles 1 mol Moles Mass (grams)

  9. Flowchart Representative Particles 1 mol______ 6.02 X 1023 particles 6.02 X 1023 particles 1 mol Moles molar mass 1 mol _____1 mol_____ molar mass Mass (grams)

  10. Mole  Mass # of moles x # of grams = mass 1 mol Example: Calculate the mass in grams of 0.0450 moles of chromium. 0.0450 molCr x 52.00 gCr = 2.34 g Cr 1 molCr

  11. Mole  MassPractice Problems • Calculate the mass of 0.625 moles of calcium. • Determine the mass of 0.187 moles of tin (II) sulfate.

  12. Mole  MassPractice Problems • Calculate the mass of 0.625 moles of calcium. Mass of Ca = mol Ca x grams Ca 1 mol Ca Mass of Ca = 0.625mol Ca x 40.078 grams Ca 1 mol Ca = 25.0 g Ca

  13. Mole  MassPractice Problems • Determine the mass of 0.187 moles of tin (II) sulfate. Mass of SnSO4 = mol SnSO4x grams SnSO4 1 mol SnSO4 Mass of SnSO4= 0.187mol SnSO4x 214.8 grams SnSO4 1 mol SnSO4 = 40.2 g SnSO4

  14. Mass  Mole Mass x ____1 mole____ = # of moles # of grams Example: How many moles of calcium are in 525 grams of calcium? 525 gCa x 1 molCa = 13.1 mol Ca 40.08 gCa

  15. Mass  MolePractice Problems • A roll of copper wire has a mass of 848 g. How many moles of copper are in the roll? • At 4.0°C, water has a density of 1.000g/ml. How many moles of water are in 1.000 kg of water?

  16. Mass  MolePractice Problems • A roll of copper wire has a mass of 848 g. How many moles of copper are in the roll? Mass Cux ____1 mole_Cu___=# of moles Cu # of grams Cu • 848 g Cux ____1 mole_Cu___=13.3 moles Cu • 63.546 g Cu

  17. Mass  MolePractice Problems • At 4.0°C, water has a density of 1.000g/ml. How many moles of water are in 1.000 kg of water? Mass H2Ox ____1 mole_ H2O ___=# of moles H2O # of grams H2O 1.000 x 103 g H2Ox ____1 mole_ H2O __=55.51 moles H2O18.015 g H2O

  18. Mass  Atoms Mass x ____1 mole____ x 6.02 x 1023 atoms = # of atoms # of grams 1 mole Example: How many atoms of gold are in a pure gold nugget having a mass of 25.0 grams? 25.0 gAu x 1 molAu x 6.02 x 1023 atomsAu = 7.65 x 1022 atoms Au 196.69 gAu 1 molAu

  19. Mass  AtomsPractice Problems Mass x ____1 mole____ x 6.02 x 1023 atoms = # of atoms # of grams 1 mole Practice: How many atoms of lead are in 4.77 g of lead? How many molecules of benzene are in 17.2 g of benzene (C6H6)?

  20. Mass  AtomsPractice Problems Mass x ____1 mole____ x 6.02 x 1023 atoms = # of atoms # of grams 1 mole How many atoms of lead are in 4.77 g of lead ? 4.77 gPb x 1 molPb x 6.02 x 1023 atomsPb = 1.38 x 1022 atoms Pb 207.2 gPb 1 molPb How many molecules of benzene are in 17.2 g of benzene (C6H6) ? 17.2 gC6H6 x 1 molC6H6 x 6.02 x 1023 molecC6H6 = 1.33 x 1023 molec 78.11 gC6H61 molC6H6 C6H6

  21. Atoms  Mass # of atoms x ____1 mole____ x # of grams = Mass 6.02 x 1023 atoms 1 mole Example: A party balloon contains 5.50 x 1022 atoms of helium gas. What is the mass in grams of the helium? 5.50 x 1022 atomsHe x 1 molHe x 4.00 g He= 0.366 g He 6.02 x 1023 atomsHe 1 molHe

  22. Atoms  MassPractice Problem # of atoms x ____1 mole____ x # of grams = Mass 6.02 x 1023 atoms 1 mole Practice: How many grams of mercury are in 1.19 x 1023 atoms of mercury gas? 1.19 x 1023 atomsHg x 1 molHg x 200.59 g Hg= 39.7 g 6.02 x 1023 atomsHg 1 molHg Hg

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