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Chemistry Mole Calculations The Mole & Molar Mass

Chemistry Mole Calculations The Mole & Molar Mass. PERIODIC TABLES NEEDED CALCULATORS NEEDED Objective: SWBAT use atomic molar masses to calculate molecular molar masses. Do Now: What is the molar mass of oxygen in grams?. The Mole - VIDEO.

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Chemistry Mole Calculations The Mole & Molar Mass

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  1. ChemistryMole CalculationsThe Mole & Molar Mass PERIODIC TABLES NEEDED CALCULATORS NEEDED Objective: SWBAT use atomic molar masses to calculate molecular molar masses. Do Now: What is the molar mass of oxygen in grams?

  2. The Mole - VIDEO • In order to perform quantitative chemistry (that is, chemistry with numbers), we need the ability to count atoms. • Unfortunately, atoms are very small. • If there were a way to know how many atoms were in a real-life large sample, calculations would be much easier.

  3. Avogadro’s Number and the Mole • Amedeo Avogadro • Experiments involving gases showed that the number of particles of gas at a given temperature and pressure didn’t change with the identity of the gas. • In a 22.4 liter container at room temperature, it was calculated that there were 6.02 x 1023 molecules inside.

  4. Avogadro’s Number and the Mole • We define one mole of atoms to be Avogadro’s number of atoms. • 1 mol = 6.02 x 1023 • Officially, a mole is defined to be the number of atoms in exactly 12 grams of carbon-12. • VIDEO – A Mole is a Unit

  5. Molar Mass • The mass of one mole of an element is called the molar mass of that element. • It is defined in terms of the element’s atomic mass (which is different from mass number… remember) • Carbon’s atomic mass: 12.0107 amu • Carbon’s molar mass: 12.0107 grams • One mole of carbon has a mass of 12.0107 grams… • This means that if you measure 12.0107 grams, you have 6.02 x 1023 atoms of carbon.

  6. Molar Mass • In one mole of carbon dioxide, CO2… • How many moles of elemental carbon are there? • How many moles of oxygen are there? • How many molecules of carbon dioxide? • How many atoms of carbon? • How many atoms of oxygen?

  7. Molar Mass • In one mole of carbon dioxide, CO2… • How many moles of elemental carbon are there? • 1 • How many moles of oxygen are there? • 2 • How many molecules of carbon dioxide? • 6.02 x 1023 • How many atoms of carbon? • 6.02 x 1023 • How many atoms of oxygen? • 1.20 x 1024 (2 x 6.02 x 1023)

  8. Molecular Molar Mass • Just like we can find the molar mass of an element, we can find the molar mass of a compound. • What is the molar mass of hydrogen? • 1.00794 g/mol • Units of grams per mole • What is the molar mass of oxygen? • 15.9994 g/mol • In this class, it is acceptable to round molar masses to the tenths place.

  9. Molecular Molar Mass • Now, to find the molar mass of H2O. • Every mole of H2O has… • 2 mol of H • 1 mol of O • The molar mass of a compound is the sum of the molar masses of its elements. • MM H2O = 2(MM H) + 1(MM O) • MM H2O = 2(1.0 g/mol) + 1(16.0 g/mol) • MM H2O = 18.0 g/mol • 18 grams of water = 1 mol water = 6.02 x 1023 molecules of water

  10. Molecular Molar Mass • Now, to find the molar mass of H2O. • Every mole of H2O has… • 2 mol of H • 1 mol of O • The molar mass of a compound is the sum of the molar masses of its elements. • MM H2O = 2(MM H) + 1(MM O) • MM H2O = 2(1.0 g/mol) + 1(16.0 g/mol) • MM H2O = 18.0 g/mol • 18 grams of water = 1 mol water = 6.02 x 1023 molecules of water

  11. Practice - Easy • What is the molar mass of carbon dioxide, CO2? • How many molecules of carbon dioxide are in this amount?

  12. Practice - Easy • What is the molar mass of carbon dioxide, CO2? • 44.0 g/mol • How many molecules of carbon dioxide are in this amount? • 6.02 x 1023 molecules

  13. Practice - Medium • What is the molar mass of barium sulfate, BaSO4?

  14. Practice - Medium • What is the molar mass of barium sulfate, BaSO4? • 233.4 g/mol • Neat Website: http://www.webqc.org/mmcalc.php • Can use to check your work!

  15. Practice - Hard • What is the molar mass of iron (III) nitrate?

  16. Practice - Hard • What is the molar mass of iron (III) nitrate, Fe(NO3)3? • 241.9 g/mol

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