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Learn about moles, molarity, and calculations in this University of Lincoln presentation under Creative Commons license. Explore the concepts of the mole, relative atomic and molecular masses, molar concentrations, and how to calculate molarity with examples provided. Acknowledgements to JISC, HEA, and others.
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Structure of matter seminar: moles and molarity University of Lincoln presentation This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
The mole Definition: 1 mole of any substance contains 6.022x1023atoms and/or molecules Amadeo Carlo Avogadro (1776-1856) 6.022 x 1023 This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
For Elements: The relative atomic mass, Ar = mass of 1 mole of atoms in grams (g) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
For Molecules: The relative molecular mass, Mr = sum of all Ar in the molecule = mass of 1 mole of molecules (g) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
Molar Concentrations, M A molar solution (1M) is a solution containing 1 mole of substance (solute) in every litre of solvent This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
Molarity The molarity of a solution is the concentration of the solution expressed as: the number of moles per litre – M or mol L-1 or mol dm-3 (all of these are the same) This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
Molarity How to calculate the molarity: • Calculate how many moles there are in solution • Work out how many moles there are per ml • X 1000 to give the number of moles per litre This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
Example 1 22 g of CaCO3 was dissolved in water and made up to give a total volume of 200 cm3. C Calculate the concentration of the solution in mol dm-3. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
Example 1 1. No mols of CaCO3 in solution = 22g/100 = 0.22 mols 2. No mols/ml = 0.22/200 = 0.0011 (= 1.1 x 10-3) 3. 1.1 x 10-3 x 1000 = 1.1M This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
Example 2 If we take 15ml of our 1.1M CaCO3 solution and make it up to 250ml with H2O, what is the concentration of the new dilution? This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
Example 2 • No. mols in 15 ml of 1.1M solution = = 1.1 x 15 = 0.0165 mols 1000 • This is put into 250 ml. No. mols per ml = 0.0165/250 = 6.6 x 10-5 • 6.6 x 10-5 x 1000 = 0.066M 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: V1 C1 = V2 C2 15 ml x 1.1 M = 250 ml x C2 C2 = 15 ml x 1.1 M = 0.066 M 250 ml This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License
Acknowledgements • JISC • HEA • Centre for Educational Research and Development • School of natural and applied sciences • School of Journalism • SirenFM • http://tango.freedesktop.org This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License