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THE MOLE

THE MOLE. MEASURING MATTER. 3 ways to measure things: count : 1 dozen = 12 apples mass : 1 dozen = 2 kg of apples volume : 1 dozen = 0.20 bushel (for typical wicker basket) We need to measure ATOMS!. MASS OF 1 CARBON ATOM. 1 amu = one proton or one neutron = 1.66 x 10 -24 g

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THE MOLE

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  1. THE MOLE

  2. MEASURING MATTER 3 ways to measure things: count: 1 dozen = 12 apples mass: 1 dozen = 2 kg of apples volume: 1 dozen = 0.20 bushel (for typical wicker basket) We need to measure ATOMS!

  3. MASS OF 1 CARBON ATOM 1 amu = one proton or one neutron = 1.66 x 10-24 g carbon has 12 protons & neutrons mass of one C atom = 1.995 x 10-23 g IMPOSSIBLE, IMPRACTICLE!

  4. MASS OF 1 CARBON ATOM One atom cannot be weighed. Can we weigh many atoms and still compare one atom to another? …

  5. MASS RATIO: He vs. N 1 atom He = 4 amu N = 14 amu 2 atoms 8 amu 28 amu 10 atoms 40 amu 140 amu 100 atoms 400 amu 1400 amu Mass ratio ( 2 : 7 ) is always the same!

  6. AVOGADRO’S NUMBER 1 carbon atom = 12.01 amu ?? atoms = 12.01 grams of carbon ANSWER: 6.02 x 1023 atoms! Avogadro’s number: number of atoms whose mass in grams = mass of one atom in amu

  7. AVOGADRO’S NUMBER We call this number of “things” one MOLE: • 6.02 x 1023 “things” = 1 mole • just like 12 “things” = 1 dozen

  8. “THINGS”:REPRESENTATIVE PARTICLES 1 mole = 6.02 x 1023 representative particles 1 mole carbon = 6.02x1023 atoms 1 mole CO2 = 6.02x1023 molecules 1 mole NaCl = 6.02x1023 formula units

  9. THE MOLE ANDMOLAR MASS 1 atom of hydrogen = 1.01 amu 6.02x1023 atoms of H = 1.01 grams 1 mole of H = 1.01 grams usually written as: 1.01 g/mole This number is called the MOLAR MASS of hydrogen.

  10. MOLAR MASS In textbook: gram atomic mass gram molecular mass gram formula mass ALL mean the same – the mass of one mole of a substance: MOLAR MASS

  11. MOLAR MASS carbon: MM = 12.01 g/mole 12.01 g = 1 mole = 6.02x1023atoms magnesium: MM = 24.34 g/mole 24.34 g = 1 mole = 6.02x1023atoms 1 mole = same number of atoms = different number of grams

  12. MOLAR MASS What is the molar mass of sulfur? 32.07 g/mole What is the molar mass of SO3? 80.07 g/mole What is the molar mass of NaCl? 58.44 g/mole

  13. AMADEO AVOGADRO

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