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Unlocking the Mole Concept in Chemistry

Dive into the fascinating world of moles and Avogadro's number used in chemistry. Learn mole conversions, molar mass calculations, and solving molar equations with examples for elements and compounds.

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Unlocking the Mole Concept in Chemistry

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  1. The MOLE

  2. ? Mole The mole is a word that means a very specific number. We know about the word “dozen” it means 12 items. The mole means 6.0221367 x 1023 particles. we just round it to 6.022 x 1023.

  3. If we have a mole of anything we have 6.022 x 1023 of them. That’s a lot of anything to have, unless you think about atoms and molecules. 1 mole of particles = 602,213,670,000,000,000,000,000 particles The number has made me crazy.

  4. Avogadro’s number Avogadro's number and is denoted by NA. It is derived from exactly 12 grams of carbon-12. 12 grams of carbon-12 has approximately 6.02 x 1023 atoms. Amadeo Avogadro (1776-1856)

  5. What do we do with it? It happens to be the SI unit of amount of anything. We use it in chemistry when working with chemical equations. It can stand for: atoms, molecules, or formula units.

  6. The mass of a mole of any one element is equal to its atomic mass. So… 1 mole “C” = 6.02 x 1023 “C” atoms = 12.01 grams Carbon

  7. Conversion Factors 1 mole C 6.02 x 1023 atoms 1 mole C 12.01 g 6.02 x 1023 atoms 12.01 g All of these can be filled around to make 3 more conversion factors, for a total of 6.

  8. Dimentional Analysis What is the mass of 2.5 moles of aluminum? We look on the Periodic table to find the atomic mass of Al. This tells us that 1 mole of Al = 26.98 grams. Time for math: 2.5 moles Al x 26.98 g = 67.45 g of Al 1 mole of Al

  9. The Key For an example lets use gold (Au). [1 mole of Au = 6.02 x 1023atoms of Au = 196.97 grams of Au] These three numbers are all we need to solve any molar equations dealing with gold. • Examples: • What is the mass of 4.5 moles of Au? • How many atoms of Au will have a mass of 89.60g? • How many moles of gold do you have if you have 5.24 x 1026 atoms of gold? • What will be the mass of 5.24 x1026 atoms of Gold?

  10. What is the mass of 4.5 moles of Au? 4.5 mol Au x 196.97 g = 886.36 g Au 1 mol Au 1 mole of Au = 6.02 x 1023 atoms of Au = 196.97 grams of Au

  11. How many atoms of Au will have a mass of 89.60g? 89.60g Au X 6.02x1023Au atoms = 2.738 x1023atoms Au 196.97 Au You are going to need one of these! 1 mole of Au = 6.02 x 1023 atoms of Au = 196.97 grams of Au

  12. Molar mass of an ionic compound & Molar mass of a molecular compound

  13. We have reviewed the mole concept for a single element (gram atomic mass or gam). Example: Na: 1mole = 22.99g or we could put it like this 22.99g Na/1 mole Na

  14. Mole of a compound: Ionic & molecular Consider NaCl Na has a molar mass of 22.99 g/mol Cl has a molar mass of 35.45 g/mol 22.99 + 35.45 58.44 g/mol We would say that the gfm (gram formula mass) of NaCl is 58.44g/mol gfm is the same thing as molar mass, but it goes with ionic compounds. So what is the molar mass of NaCl?

  15. More examples: One way to determine the molar mass is like this: Fe2O3 Iron (III) oxide

  16. More examples: Zn(OH)2 “Zinc hydroxide” 99.39 The gfm or molar mass of zinc hydroxide is 99.39g/mol

  17. What about molecular compounds Its really the same way! How about water (H2O)? You calculate it.

  18. Conversion factors 1 mole H2O = 18.00 grams = 6.02 x 1023 molecules of H2O 1 mole H2O 18.00g H2O 18.00 g H2O 6.02 x 1023 molecules 18.00 g H2O 1 mole Q. What is the mass of 2.5 moles of water? 18.00 g H2O = 1 mole H2O 45.00g H2O 2.5 moles of H2O x

  19. Mass to moles How many moles of silver nitrate (AgNO3) will have a mass of 55.0g? 1st find gfm of AgNO3 Ag 1 x 107.87 = 107.87 N 1 x 14.01 = 14.01 O 3 x 16.00 = + 48.00 169.88 g/mol 55.0g AgNO3 x 1 mole AgNO3 = 169.88 g AgNO3 0.324 mole AgNO3

  20. Page 340 in chemistry text.

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