THE MOLE

THE MOLE

Moles of a mass
1. Moles = Mass/Mr
  1. E.G 2.4 Magnesium= 2.4/24= 0.1 moles
2. 1 Mole of any substance contains the same number of particles, this number is 6.0x10(23)
  1. This is Avogadro's number
3. Mass= Moles x Mr
Moles of a Solution
1. Moles = concentration/Volume
  1. Units of concentration = mol/dm(3)
  2. Unit of volume = dm(3)
  3. E.G 25cm(3) of 0.100 mol/dm(3) of Sodium solution = (0.100 x 25) / 1000 = 2.5x10(-3)
2. Most experiments do not use 1dm(3) of solution, much smaller volumes are used, therefore you must convert cm(3) to dm(3)
  1. 1 dm(3) = 1000 cm(3)
    1. To convert cm(3) to dm(3) divide by 1000
      1. Or moles = (conc x vol)/1000
Moles of Gases
1. Moles = Volume (dm3) / 24 (dm3)
  1. OR Moles = volume (cm3) / 24,000 (cm3)
2. One mole of any gas at room temp and pressure has the volume of 24(dm3)
Yield
1. The amount of a product obtained from a chemical reaction is known as the yield
  1. Percentage yield is easier to talk about.
    1. This compares the amount of product that the reaction really produces with the maximum amount that it could possibly be
2. % Yield = (amount of product actually made / Maximum amount of product possible) x 100
3. No atoms are lost or gained, it is not always possible to obtain the calculated amount of yield.
  1. This is because:
    1. The reactions may not be completely pure
    2. The reaction may not go to completion because it is reversible
    3. Some of the product may be left behind in the apparatus
    4. Some of the product may be lost when it is separated from the reaction mixture of its other products
    5. Some of the reactants may react in ways different to the expected reaction to give unexpected products.

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