What is a Mole?
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- 2. What is a counting unit? You’re already familiar with one counting unit…a “dozen” A dozen = 12 “Dozen” 12 A dozen doughnuts 12 doughnuts A dozen books 12 books A dozen cars 12 cars A dozen people 12 people
- 3. OTHER COUNTING UNITS • pair = 2 • trio = 3 • quartet = 4 • dozen = 12 eggs • gross = 144 pencils • ream = 500 paper • mole (mol) = 602000000000000000000000 • =6.02x1023 3
- 4. AVOGADRO’S NUMBER 6.02x1023 4
- 5. Avogadro’s number The number of particles in one mole is called Avogadro’s number. It is named after Amedeo Avogadro, an Italian scientist working in the early 19th century. mantle 6.02 × 1023 really is a crust staggeringly large number of particles. marbles If you collected 6.02 × 1023 marbles and spread them over the surface of the Earth, they would form a layer of marbles 50 miles thick! 5 of 12 © Boardworks Ltd 2009
- 6. HOW BIG IS A MOLE? • There are ~ 6.6 billion people on Earth • How many Earths would it take to equal the population of 1 mole? 9.12 x 1013 6
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- 8. • If you had a mole of cats . . . • They would create a sphere larger than the Earth! 8
- 9. • If you had a mole of $$$$$ and you spent $800 billion dollars a day how many years would it take to spend a MOLEion dollars? 2,060,000,000 years 9
- 10. • If you had a mole of H2O could you swim in it? NO! • Water molecules are so small that a mole of H2O = 18mL • This means a 12 ounce bottle of water would have 19.7 “moles” of water…a much easier-to-work-with number! 10
- 11. HOW SMALL ARE ATOMS? • There are more atoms in one gram of salt than grains of sand on all the beaches of all the oceans in all the world. 11
- 12. • Just one grain of sugar contains 1 x 10 17 molecules • Each time you take a breath of air, you inhale about • 2 x 1022 molecules of nitrogen and • 5 x 1021 molecules of oxygen. 12
- 13. How many particles? Scientists often need to know how many particles of a substance they are dealing with. Unfortunately, atoms and molecules are tiny and it is impossible to count …thirty-four them directly. million and one… In chemistry we don’t work with individual atoms or molecules because they are too small to be weighed or measured 13 of 12 © Boardworks Ltd 2009
- 14. • We have to work with LOTS of atoms in order to measure them • THAT’s WHERE THE MOLE COMES IN! 14
- 15. MOLAR MASS IS • The mass in grams of 1 mole of atoms of an element • In other words…… 1 mol C atoms = 6.02 x 1023 C atoms = 12g C 15
- 16. How much is in a mole? One mole of carbon weighs 12 g, so 12 g of carbon contains 6.02 × 1023 carbon atoms. One mole of sodium weighs 23 g, so 23 g of sodium contains 6.02 × 1023 sodium atoms. One mole of water weighs 18 g, so 18 g of water contains 6.02 × 1023 water molecules. How many carbon atoms are in 6 g of carbon? 3.01 × 1023 16 of 12 © Boardworks Ltd 2009
- 17. Mass for 1 mole of atoms The average atomic mass = grams for 1 mole Average atomic mass is found on the periodic table Element Mass 1 mole of carbon atoms 12.01 g 1 mole of oxygen atoms 16.00 g 1 mole of hydrogen 1.01 g atoms Unit for molar mass: g/mole or g/mol
- 18. MASS-MOLE PROBLEMS….. • Ifyou start with Moles, Multiply • Ifyou Don’t, Divide 18
- 19. MOLE – MASS RELATIONSHIPS Practice 19
- 20. Practice 1 • What is the mass, in grams, of 2 moles of carbon? • ANS: 2 mol C x 12 g/mol = 24 g Molar Mass from Periodic Table 20
- 21. Practice 2 • What is the mass, in grams, of 5 moles of iron? • ANS: 5 mol Fe x 55.8 g/mol = 279 g 21
- 22. Practice 3 • How many moles are in a 64-gram sample of pure sulfur? • ANS: 64 grams S = 2.0 mol 32.1 g/mol Molar Mass from Periodic Table 22
- 23. Practice 4 • How many moles are in a 72-gram sample of pure magnesium? • ANS: 72 grams Mg = 2.96 mol 24.3 g/mol 23