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Chemical Quantities

Chemical Quantities. When small amounts of substances are being used in chemistry very large numbers of particles are involved. Chemical Quantities. One teaspoon of copper sulfate…. Contains 3.0 x 10 22 Cu 2+ and SO 4 2- ions . 30,000,000,000,000,000,000,000 ions.

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Chemical Quantities

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  1. Chemical Quantities Whensmall amounts of substances are being used in chemistry very large numbers of particles are involved.

  2. Chemical Quantities One teaspoon of copper sulfate… Contains 3.0 x 1022Cu2+ and SO42- ions. 30,000,000,000,000,000,000,000ions.

  3. Chemical Quantities One cup of water… Contains 5.30 x 1024water molecules 5,300,000,000,000,000,000,000,000 water molecules

  4. Chemical Quantities A 500mL conical flask… Contains 2.40 x 1021oxygen molecules 2,400,000,000,000,000,000,000 O2 molecules

  5. When small amounts like this are being used,how do people know the amount of particles? Chemical Quantities

  6. Do people count out everything? How does: • A builder count 5536 nails to complete a house? • An office worker count 2400 sheets of A4 paper? • A banker count a bag of $2 coins? • Somebody buy eggs or socks? • Somebody count the amount of cards in two packs?

  7. Chemical Quantities Chemist need a convenient method to count the number of particles (atoms, molecules, ions etc). Because atoms are so small and there are so many of them in even the smallest sample, it is impossible to count them directly. So chemists created the counting unit called the mole.

  8. The Mole The mole , symbol mol is the basic SI unit used to measure the chemical amount of a substance. The mole is defined: “as the number of atoms present in exactly 12 g of the carbon-12 isotope”

  9. The Mole And… there are 6.02 x 1023 602,000,000,000,000,000,000,000 atoms in 12 g of the carbon-12 isotope

  10. The Mole So… 1 mol = 6.02 x 1023particles

  11. The Mole So a mole of anything contains 6.02 x 1023 particles and this number has a special name called Avogadro’s number (NA) NA = 6.02 x 1023 particles = 1 mol

  12. Mole Examples Example.. • 1 molof carbon contains 6.02 x 1023 carbon atoms. • 0.50 mol of CO2 contains () = 3.00 x 1023CO2 molecules. • 1 molof methane, CH4, contains 6.02 x 1023 carbon atomsand (4 x 6.02 x 1023) = 2.41 x 1024 hydrogen atoms.

  13. Avogadro’s Number, NA Is so large that… 1 molof marbles would cover the surface of the Earth to a depth of more than 6km.

  14. Avogadro’s Number, NA

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