2011 topic 01 lecture 1 - the mole and avogadro's constant


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2011 topic 01 lecture 1 - the mole and avogadro's constant

  1. 1. IB Chemistry Power Points<br />Topic 1<br />Quantitative Chemistry<br />www.pedagogics.ca<br />Lecture 1<br />The Mole and Avogadro’s Constant<br />
  2. 2. The Structure of Matter<br />Matter<br />Pure Substances<br />Mixtures<br />Solutions<br />Elements<br />Compounds<br />Covalent<br />Ionic<br />Atoms<br />Molecules<br />Formula Units<br />Fundamental “particles” of pure substances<br />
  3. 3. Elements - Metals<br />Structure of metallic elements<br />The metal solids “particles” consist of individual metal ions held together by mutual attraction for each others valence electrons.<br />
  4. 4. Elements – Noble Gases<br />The noble gases are the Group 8 (18) elements: He, Ne, Ar, Kr, Xe and Rn. They are extremely unreactive – considered to be inert. <br />The fundamental particles of these elements are single atoms (monatomic).<br />
  5. 5. Elements – Diatomic Molecules<br />Seven elements (H, N, O, F, Cl, Br, and I) are called the diatomic elements because, as pure elements, they form molecules containing two atoms. <br />Different representations of Cl2<br />The fundamental particles of these elements are molecules. Each molecule contains only one type of atom.<br />
  6. 6. Elements – Other Structures<br />Carbon and silicon exist as giant covalent structures – networks of atoms held together by covalent bonds.<br />Other non-metallic elements are found in molecular form.<br />
  7. 7. Compounds – Molecular Covalent<br />Covalent compounds consist of groups of two or more different types of atoms bonded together into particles called molecules.<br />Water is molecular covalent compound consisting of H2O molecules.<br />
  8. 8. Do not confuse the forces BETWEEN molecules with the bonds WITHIN molecules<br />covalent bonds hold hydrogen and oxygen atoms together to make water molecules<br />intermolecular forces exist between adjacent H2O molecules<br />
  9. 9. Compounds – Simple Ionic<br />Ionic compounds consist of groups of ions held together by electrostatic attractions. Atoms lose or gain electrons to form cations and anions. The fundamental particle is called a formula unit.<br />Sodium chloride is an ionic compound. The chemical formula NaCl shows the 1:1 ratio of Na to Cl in compound<br />
  10. 10. Compounds – Simple Ionic<br />Two representations of NaCl<br />
  11. 11. Key Concept – “particles” is a general term referring to the fundamental components of a pure substance. This can be individual atoms, ions, small molecules, or formula units.<br />Now we can introducethe Mole<br />
  12. 12. A mole is a unit of quantity.A mole is 6.02 x 1023 things.<br />6.02 x 1023 is known as Avogadro’s constant (NA)<br />÷ 6.02 x 1023<br />Number of atoms, molecules or fundamental units<br />Number of moles (mol)<br />× 6.02 x 1023<br />
  13. 13. Why the Mole?<br />Consider one molecule of water<br />How many molecules in 2000 mL of water?<br />6.7 x 1025 molecules<br />
  14. 14. 6.7 x 1025 molecules is not a manageable number. Consider:<br />We count eggs by the dozen<br />We measure long periods of time in centuries.<br />We measure long distances in our universe using light years.<br />
  15. 15. The Mole<br />There are many ways of measuring large quantities that utilize large units. The mole is one such unit.<br />The mole is the SI unit for chemical quantity used to count the particles in a sample of pure substance.<br />One mole = 6.02x1023 particles.<br />“One mole of anything = 6.02x1023 units of that thing”<br />
  16. 16. The Mole<br />How many molecules of water in 2000 mL?<br />6.7 x 1025 molecules<br />Or 111 mol meaning 111 moles of water molecules. This is a much more manageable number.<br />
  17. 17. How many atoms are in 0.065 mol of copper?<br />3.9 x 1022<br />3.9 x 1022<br />How many molecules are in 0.065 mol of CO2?<br />3.9 x 1022<br />How many formula units are in 0.065 mol of NaCl?<br />How many moles is 9.03 x 1023 atoms of copper?<br />1.5<br />1.5<br />How many moles is 9.03 x 1023 molecules of CO2?<br />1.5<br />How many moles is 9.03 x 1023 formula units of NaCl?<br />
  18. 18. How many oxygen atoms are in 1.4 x 10-7 mol of oxygen gas (O2)?<br />(1.4 x 10-7) × NA= 8.428 x 1016 molecules of O2<br />2 atoms of oxygen per molecule sofinal answer = 1.7 x 1017 atoms of oxygen (2 SF)<br />Given 1.76 x 1012 molecules of O2, how many moles of iron III oxide (Fe2O3) can be assembled?<br />
  19. 19. Fe2O3is an example of aChemical Formulae<br />
  20. 20. 4 atoms of oxygen<br />1 atom of sulfur<br />2 atoms of hydrogen<br />What are chemical formulae?<br />● short-hand notation<br />● tells us the types of elements in a compound<br /> ● gives the number of atoms of each type of element in one molecule of the compound<br />H2SO4 sulphuric acid<br />1 molecule of H2SO4<br />
  21. 21. How many atoms in each?<br />C6H12O6 glucose<br />Mg(NO3)2 magnesium nitrate<br />Cu(SO4)2●5 H2O copper II sulfate hydrate<br />
  22. 22. Relative Molecular (Formula) Mass (MR)<br />RECALL: The average relative atomic mass (AR) for each element is noted on the Periodic Table. For example AR for copper is 63.55. Relative masses are based on 1/12th the mass of a 12C atom.<br />The relative molecular mass is the total mass of the atoms in one molecule or formula unit of a particular compound relative to carbon-12.<br />For example H2SO4:<br />Hydrogen 2 atoms × 1.01 = 2.02<br />Sulfur 1 atom × 32.07 = 32.07<br />Oxygen 4 atoms × 16.00 = 64.00 <br />MR 98.09<br />
  23. 23. Molar MassAre you sitting comfortably?<br />
  24. 24. Mass and the Mole: Why 6.02×1023?<br />1 mole = 6.02×1023 was chosen because this was then number of carbon-12 atoms that has a mass of 12 grams.<br />Pure carbon (a mix of isotopes) has a mass of 12.01 g per mole.<br />We call this value MOLAR MASS<br />Consider1 atom of sulfur AR = 32.07 = 5.326×10-23 grams<br />Consider1 mole of sulfur = 6.02×1023 atoms = 32.07 grams<br />
  25. 25. 6.02×1023 is a REALLY BIG number<br />Consider 6.02×1023sheets of paper stacked. <br />How many round trips to the Moon would this stack of paper be equivalent to? <br />8×1010 (eighty billion ) roundtrips. Create, pick, find a mole analogy of your own. Show the math.<br />
  26. 26. MOLARMASS<br />Language issuegram atomic massgram molecular massgram formula mass<br />Aluminum AR = 26.98 gram atomic mass = 26.98 g mol-1<br />Carbon dioxide (CO2) MR = 44.00 gram molecular mass = 44.00 g mol-1<br />Sodium chloride (NaCl) MR= 58.44 gram formula mass = 58.44 g mol-1<br />
  27. 27. We weigh chemical quantities in grams. The molar mass value for a substance allows us to determine the number of moles from a measured mass.<br />Consider 5.68 g of MgCl2<br />Molar mass of MgCl2 = 95.21 g mol-1<br />
  28. 28. ÷ 6.02 x 1023<br />× molar mass<br />Number of atoms, molecules or fundamental units<br />MOLES<br />MASS<br />× 6.02 x 1023<br />÷ molar mass<br />
  29. 29. 1. How many moles are in 45.0 g of water?<br />2.50 mol<br />77.0 g<br />2. What is the mass of 1.75 mol of CO2?<br />9 moles<br />3. How many moles of oxygen atoms are in 300 g of CaCO3?<br />95.3 g<br />4. What is the mass of 9.03 x 1023 atoms of copper?<br />0.589 mol<br />5. 106 g of glucose (C6H12O6) is how many moles?<br />56.5 g<br />6. What is the mass of the oxygen atoms in 106 g of glucose?<br />