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Chapter 11 Mathematics & Chemical Formulas

Chapter 11 Mathematics & Chemical Formulas. Unit 6 – The Mole. Atoms are too small/light. Atoms are too small and too light to count or mass as individuals One Carbon-12 atom = 1.99 x 10 -23 grams We use this as the basis for atomic mass units . 1 Carbon atom is 12 amu .

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Chapter 11 Mathematics & Chemical Formulas

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  1. Chapter 11 Mathematics & Chemical Formulas Unit 6 – The Mole

  2. Atoms are too small/light • Atoms are too small and too light to count or mass as individuals • One Carbon-12 atom = 1.99 x 10-23 grams • We use this as the basis for atomic mass units. • 1 Carbon atom is 12 amu. • 6 protons + 6 neutrons = 12 “things” that make up the mass of a carbon atom • One amu = 1/12 of a carbon atom

  3. Atomic Mass & Formula Mass • Atomic mass - the mass of 1 mole of atoms (also known as “molar mass”) • Formula mass - the masses of all the atoms in an ionic compound. Ex: CaCl2 • Molecular Mass – the masses of all of the atoms in a molecular compound. Ex: CH4

  4. Formula Weight (FW) • So, the formula weight of calcium chloride, CaCl2, would be Ca: 1(40.1 amu) + Cl: 2(35.5 amu) 111.1 amu • To convert to molar mass, change amus to g/mol. 1 amu = 1 g/mol

  5. + H: 4(1.0 amu) Molecular Weight (MW) • For the molecule methane, CH4, the molecular weight would be C: 1(12.0 amu) 16.0 amu The molar mass of methane would be 16.0 g/mol

  6. 1 mole - different physical states Moles provide a bridge from the molecular scale to the real-world scale.

  7. Examples of Molar Mass • List the molar masses of the following: • Zn • CuSO4 • NaCl • H2O • Al2(SO4)3

  8. The Mole – a word that means a # • Other words that mean #s: • One dozen = • 12 • One gross = • 144 • One score = • 20 • One ream = • 500 • One MOLE = 6.02 x 1023 • 602000000000000000000000

  9. Where does Avogadro’s Number come from? • A formula: M = NAmC The mass of 1 carbon-12 atom is 1.99 x 10-23 g

  10. Avogadro’s Number • Avogadro’s Number - 6.02 x 1023 particles in 1 mole • 1 mole of 12C has a mass of 12 g.

  11. Mole Conversions • Moles tell you how many atoms you have, AND how much mass in grams you have. • We use moles to convert from atoms and grams.

  12. Mole Conversion Factors • There are 4 possible conversion factors for mole conversions: • Show your work -use a conversion factor every time

  13. Mole Diagram – Conversion Factors

  14. Using your calculator • To Enter 6.02 x 1023 into your calculator, use the EE button, so it would appear as 6.02E23. Practice with the two following examples

  15. If you have 4.25 x 1022 atoms of Al, how many moles do you have? If you have 0.37 moles of Al, how many atoms do you have? Examples:

  16. Mole Examples (lol) • If you have 8.64g of Mg, how many moles do you have? • If you have 1.23 moles of Phosphorous, how many grams do you have?

  17. Mole Relationships • One mole of: • atoms • ions • molecules • contains Avogadro’s number of those particles. • One mole of: • molecules or formula units • contains Avogadro’s number times the number of atoms or ions of each element in the compound.

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