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THE MOLE

THE MOLE. We can’t work with individual atoms or amu’s in the lab…..Why not?? Because we cannot see things that small !. Dude !!!! Atoms are REALLY REALLY small !!. We work with samples large enough for us to SEE and WEIGH on a balance using units of grams. This creates a problem….

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THE MOLE

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  1. THE MOLE

  2. We can’t work with individual atoms or amu’s in the lab…..Why not?? Because we cannot see things that small ! Dude !!!! Atoms are REALLY REALLY small !!

  3. We work with samples large enough for us to SEE and WEIGH on a balance using units of grams.

  4. This creates a problem….. A pile of atoms big enough for us to see contains BILLIONS OF ATOMS !!!!

  5. SOOOOO…chemists made up a new unit…. THE MOLE

  6. A mole is the SI base unit used to measure the amount of a substance. - Its abbreviation is mol. WHAT IS A MOLE???

  7. Why is this unit necessary in chemistry?

  8. HOLY MOLE-Y ! A mole is the mass of a substance that contains a certain number of molecules (or atoms). • For example, a MOLE of carbon weighs 12 grams and is made up of…. 6.022 x 1023 particles !

  9. If I had a dozen eggs…..how many do I have?

  10. Just like a dozen represents 12….A mole represents 6.022 X 1023items, whatever they may be. • 1 mol H atoms = 6.022 x 1023 H atoms • 1 mol electrons = 6.022 x 1023 electrons • 1 mol pennies = 6.022 x 1023 pennies

  11. This number 6.022 x 1023 (NA) is known as Avogadro’s number and is one of the most fundamental constants in the field of chemistry. One mole of a substance contains 6.022 x 1023molecules.

  12. Just How Big is a Mole? • Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles. • If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles. • If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

  13. MORE MEGAMOLE FACTS! • One mole of moles, placed head to tail, would stretch 11 million light years and weigh 9/10 as much as the moon. • If a mole of pennies were evenly distributed among the world’s population, each of us would have enough money to spend $1 million dollars every hour – day and night – and still have one half of it unspent at the time of our death.

  14. Avogadro’s Number as Conversion Factor 6.02 x 1023 particles 1 mole or 1 mole 6.02 x 1023 particles Note that a particle could be an atom OR a molecule!

  15. Molar mass: the sum of atomic masses of all the atoms shown by the formula of a substance Use the periodic table to find the needed atomic weights EXAMPLE: Water (H2O) Atom# Atoms x Atomic Weight H 2 x 1.0097 amu O 1 x 15.994 amu Molar mass = 2(1.0097) + 1(15.997) = 18.0164 grams/mole = 18.016 g/mol A mole can also be calculated by the molar mass.

  16. The molar mass, in grams per mole, is numerically equal to the sum of the masses (in amu) of the atoms in the formula.

  17. Other Names Related to Molar Mass • Molecular Mass/Molecular Weight: If you have a single molecule, mass is measured in amu’s instead of grams. But, the molecular mass/weight is the same numerical value as 1 mole of molecules. Only the units are different. (This is the beauty of Avogadro’s Number!) • Formula Mass/Formula Weight: Same goes for compounds. But again, the numerical value is the same. Only the units are different. • THE POINT: You may hear all of these termswhich mean the SAME NUMBER… just different units

  18. Learning Check! Find the molar mass (usually we round to the tenths place) = 79.9 g/mole • 1 mole of Br atoms • 1 mole of Sn atoms = 118.7g/mole

  19. Molar Mass of Molecules and Compounds Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 = ????? 1 mole Ca x 40.1 g/mol + 2 moles Cl x 35.5 g/mol = 111.1 g/mol CaCl2

  20. Learning Check! • Molar Mass of K2O = ? Grams/mole

  21. Learning Check Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass.

  22. Calculations with Molar Mass molar mass Grams Moles

  23. THE END

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