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The MOLE

The MOLE. The term “MOLE” is used to count numbers of atoms and molecules A “MOLE” represents a number 6.02 x 10 23 (scientific notation). 6.02 x 10 23 - Avogadro’s Number. The mole , 6.02 x 10 23 , is referred to as Avogadro's number . 

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The MOLE

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  1. The MOLE • The term “MOLE” is used to • count numbers of • atoms and molecules • A “MOLE” represents a number • 6.02 x 1023 • (scientific notation)

  2. 6.02 x 1023 - Avogadro’s Number • The mole, 6.02 x 1023, is referred to as Avogadro's number.  • In 1811, Amadeo Avogadro, an Italian physics professor, hypothesized that “equal volumes of different gases contain equal numbers of atoms”  • Scientists later used Avogadro's • hypothesis for all molecules. • Molecular masses of all • substances contain the same • number of molecules: 6.02 x 1023.

  3. A Mole is a BIG Number • For example: • A dozen eggs will make a large omelet, • but a mole of eggs will fill all of Earth’s oceans 30 million times • It would take 12 billion chickens • laying 12 eggs per day • about 12 billion years • to lay 1 mole of eggs

  4. A Mole is a BIG Number It would take 12 billion chickens laying 12 eggs per day about 12 billion years to lay 1 mole of eggs

  5. Again, a mole is 6.02 x 1023 items • That is 602,000,000,000,000,000,000,000 • (that is 602 sextillion) • So why would we ever use such a big number?

  6. How Many in a Mole? So why would we ever use such a big number? A mole is 6.02x1023 items That is: 602, 000, 000, 000, 000, 000, 000, 000 602 sextillion!

  7. Counting Atoms and Molecules Atoms and molecules are very tiny – it takes a LOT of them to make even a single milliliter! For example, one milliliter of water would have: 3.34x1022 atoms of oxygen 6.68x1022 atoms of hydrogen

  8. “MOLE” is Used to Count Atoms and Molecules • Atoms and molecules are very tiny • it takes a LOT of molecules to make a milliliter • Instead of counting …illions and …illions • it's much simpler to count in “moles” • It’s easier to say “1 mole” • than to say • “six-hundred-and-two-sextillion”

  9. Elemental Molar Masses • For any element, the molar mass is equal to its average atomic mass. • Found on the periodic table • Measured in grams per mole (g/mol)

  10. Diatomic Elements • Most elements are listed as single atoms when in the elemental form, but seven of them are not. You need to know which elements are diatomic! • Hydrogen, Nitrogen, Oxygen, Fluorine, Chlorine, Bromine and Iodine!

  11. Diatomic Elements • Whenever one of these elements is by itself it will always be in twos! • Example: N2 is nitrogen gas • This does NOT affect these elements when they are in a compound, only when by themselves!

  12. Mole Calculations • Use dimensional analysis to solve mole problems. • Points to remember: • Always go to moles first! • Write your units at every step!

  13. Example 1 • How many moles are in 24.6 g of neon? • Neon is 20.180 g/mol

  14. Example 2 • What is the mass of 2.50 moles of hydrogen gas? • Hydrogen is diatomic, so it is H2 • Molar mass is 2.016 g/mol

  15. Example 3 • How many atoms are in 3.95 moles of beryllium?

  16. Example 4 • How many moles are in 5.15x1023 atoms of sulfur?

  17. Example 5 • What is the mass of 2.00x1024 atoms iron?

  18. Example 6 • How many atoms are in 15.4 g lithium?

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