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Chemical Structure: Structure of Matter: Seminar

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Lecture materials for the Introductory Chemistry course for Forensic Scientists, University of Lincoln, UK. See http://forensicchemistry.lincoln.ac.uk/ for more details.

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Chemical Structure: Structure of Matter: Seminar

  1. 1. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Structure of matter seminar: moles and molarity University of Lincoln presentation
  2. 2. The mole <ul><li>Definition: </li></ul><ul><li>1 mole of any substance contains </li></ul><ul><li>6.022x10 23 atoms and/or molecules </li></ul><ul><li>Amadeo Carlo Avogadro (1776-1856) </li></ul><ul><li>6.022 x 10 23 </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  3. 3. For Elements: <ul><li>The relative atomic mass, </li></ul><ul><li>A r = mass of 1 mole of atoms in grams (g) </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  4. 4. For Molecules: <ul><li>The relative molecular mass, </li></ul><ul><li>M r = sum of all A r in the molecule </li></ul><ul><li> = mass of 1 mole of molecules (g) </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  5. 5. Molar Concentrations, M <ul><li>A molar solution (1M) is a solution containing 1 mole of substance (solute) in every litre of solvent </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  6. 6. Molarity <ul><li>The molarity of a solution is the concentration of the solution expressed as: </li></ul><ul><ul><li>the number of moles per litre – </li></ul></ul><ul><ul><ul><li>M or mol L -1 or mol dm -3 </li></ul></ul></ul><ul><li>(all of these are the same) </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  7. 7. Molarity <ul><li>How to calculate the molarity: </li></ul><ul><li>Calculate how many moles there are in solution </li></ul><ul><li>Work out how many moles there are per ml </li></ul><ul><li>X 1000 to give the number of moles per litre </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  8. 8. Example 1 <ul><li>22 g of CaCO 3 was dissolved in water and made up to give a total volume of 200 cm 3 . C </li></ul><ul><li>Calculate the concentration of the solution in mol dm -3 . </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  9. 9. Example 1 <ul><li>1. No mols of CaCO 3 in solution = </li></ul><ul><li>22g/100 = 0.22 mols </li></ul><ul><li>2. No mols/ml = 0.22/200 = 0.0011 </li></ul><ul><li> (= 1.1 x 10 -3 ) </li></ul><ul><li>3. 1.1 x 10 -3 x 1000 = 1.1M </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  10. 10. Example 2 <ul><li>If we take 15ml of our 1.1M CaCO 3 solution and make it up to 250ml with H 2 O, what is the concentration of the new dilution? </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  11. 11. Example 2 <ul><li>N o . mols in 15 ml of 1.1M solution = </li></ul><ul><ul><ul><ul><li>= 1.1 x 15 = 0.0165 mols </li></ul></ul></ul></ul><ul><ul><ul><ul><li>1000 </li></ul></ul></ul></ul><ul><li>This is put into 250 ml. N o . mols per ml = 0.0165/250 = 6.6 x 10 -5 </li></ul><ul><li>6.6 x 10 -5 x 1000 = 0.066M </li></ul>This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
  12. 12. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Alternatively You can use the following formula: V 1 C 1 = V 2 C 2 15 ml x 1.1 M = 250 ml x C 2 C2 = 15 ml x 1.1 M = 0.066 M 250 ml
  13. 13. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Acknowledgements <ul><li>JISC </li></ul><ul><li>HEA </li></ul><ul><li>Centre for Educational Research and Development </li></ul><ul><li>School of natural and applied sciences </li></ul><ul><li>School of Journalism </li></ul><ul><li>SirenFM </li></ul><ul><li>http://tango.freedesktop.org </li></ul>

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