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Chapter 6

Chapter 6. Chemical Quantities. How you measure how much?. You can measure mass, or volume, or you can count pieces. We measure mass in grams. We measure volume in liters. We count pieces in MOLES. Moles. Defined as the number of carbon atoms in exactly 12 grams of carbon-12.

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Chapter 6

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  1. Chapter 6 Chemical Quantities

  2. How you measure how much? • You can measure mass, • or volume, • or you can count pieces. • We measure mass in grams. • We measure volume in liters. • We count pieces in MOLES.

  3. Moles • Defined as the number of carbon atoms in exactly 12 grams of carbon-12. • 1 mole is 6.02 x 1023 particles. • Treat it like a very large dozen • 6.02 x 1023 is called Avogadro’s number.

  4. Representative particles • The smallest pieces of a substance. • For a molecular compound it is a molecule. • For an ionic compound it is a formula unit. • For an element it is an atom.

  5. Types of questions • How many oxygen atoms in the following? • CaCO3 • Al2(SO4)3 • How many ions in the following? • CaCl2 • NaOH • Al2(SO4)3

  6. Types of questions • How many molecules of CO2 are the in 4.56 moles of CO2 ? • How many moles of water is 5.87 x 1022 molecules? • How many atoms of carbon are there in 1.23 moles of C6H12O6 ? • How many moles is 7.78 x 1024 formula units of MgCl2?

  7. Measuring Moles • Remember relative atomic mass? • The amu was one twelfth the mass of a carbon 12 atom. • Since the mole is the number of atoms in 12 grams of carbon-12, • the decimal number on the periodic table is also the mass of 1 mole of those atoms in grams.

  8. Gram Atomic Mass • The mass of 1 mole of an element in grams. • 12.01 grams of carbon has the same number of pieces as 1.008 grams of hydrogen and 55.85 grams of iron. • We can write this as 12.01 g C = 1 mole • We can count things by weighing them.

  9. Examples • How much would 2.34 moles of carbon weigh? • How many moles of magnesium in 24.31 g of Mg? • How many atoms of lithium in 1.00 g of Li? • How much would 3.45 x 1022 atoms of U weigh?

  10. What about compounds? • in 1 mole of H2O molecules there are two moles of H atoms and 1 mole of O atoms • To find the mass of one mole of a compound • determine the moles of the elements they have • Find out how much they would weigh • add them up

  11. What about compounds? • What is the mass of one mole of CH4? • 1 mole of C = 12.01 g • 4 mole of H x 1.01 g = 4.04g • 1 mole CH4 = 12.01 + 4.04 = 16.05g • The molecular mass of CH4 is 16.05g • The mass of one mole of a molecular compound.

  12. Gram Formula Mass • The mass of one mole of a compound. • Calculated the same way. • What is the GFM of Fe2O3? • 2 moles of Fe x 55.85 g = 111.70 g • 3 moles of O x 16.00 g = 48.00 g • The GFM = 111.70 g + 48.00 g = 159.70g

  13. Molar Mass • The generic term for the mass of one mole. • The same as molecular mass, gram formula mass, and gram atomic mass.

  14. Examples • Calculate the molar mass of the following and tell me what type it is. • Na2S • N2O4 • C • Ca(NO3)2 • C6H12O6 • (NH4)3PO4

  15. Using Molar Mass Finding moles of compounds Counting pieces by weighing

  16. Molar Mass • The number of grams of 1 mole of atoms, ions, or molecules. • We can make conversion factors from these. • To change grams of a compound to moles of a compound.

  17. For example • How many moles is 5.69 g of NaOH?

  18. For example • How many moles is 5.69 g of NaOH?

  19. For example • How many moles is 5.69 g of NaOH? • need to change grams to moles

  20. For example • How many moles is 5.69 g of NaOH? • need to change grams to moles • for NaOH

  21. For example • How many moles is 5.69 g of NaOH? • need to change grams to moles • for NaOH • 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g

  22. For example • How many moles is 5.69 g of NaOH? • need to change grams to moles • for NaOH • 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g • 1 mole NaOH = 40.00 g

  23. For example • How many moles is 5.69 g of NaOH? • need to change grams to moles • for NaOH • 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g • 1 mole NaOH = 40.00 g

  24. For example • How many moles is 5.69 g of NaOH? • need to change grams to moles • for NaOH • 1mole Na = 22.99g 1 mol O = 16.00 g 1 mole of H = 1.01 g • 1 mole NaOH = 40.00 g

  25. Examples • How many moles is 4.56 g of CO2 ? • How many grams is 9.87 moles of H2O? • How many molecules in 6.8 g of CH4? • 49 molecules of C6H12O6 weighs how much?

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