THE MOLE

THE MOLE

1. Moles of a mass

   • Moles = Mass/Mr
     • E.G 2.4 Magnesium= 2.4/24= 0.1 moles
   • 1 Mole of any substance contains the same number of particles, this number is 6.0x10(23)
     • This is Avogadro's number
   • Mass= Moles x Mr

2. Moles of a Solution

   • Moles = concentration/Volume
     • Units of concentration = mol/dm(3)
     • Unit of volume = dm(3)
     • E.G 25cm(3) of 0.100 mol/dm(3) of Sodium solution = (0.100 x 25) / 1000 = 2.5x10(-3)
   • Most experiments do not use 1dm(3) of solution, much smaller volumes are used, therefore you must convert cm(3) to dm(3)
     • 1 dm(3) = 1000 cm(3)
       • To convert cm(3) to dm(3) divide by 1000
         • Or moles = (conc x vol)/1000

3. Moles of Gases

   • Moles = Volume (dm3) / 24 (dm3)
     • OR Moles = volume (cm3) / 24,000 (cm3)
   • One mole of any gas at room temp and pressure has the volume of 24(dm3)

4. Yield

   • The amount of a product obtained from a chemical reaction is known as the yield
     • Percentage yield is easier to talk about.
       • This compares the amount of product that the reaction really produces with the maximum amount that it could possibly be
   • % Yield = (amount of product actually made / Maximum amount of product possible) x 100
   • No atoms are lost or gained, it is not always possible to obtain the calculated amount of yield.
     • This is because:
       • The reactions may not be completely pure
       • The reaction may not go to completion because it is reversible
       • Some of the product may be left behind in the apparatus
       • Some of the product may be lost when it is separated from the reaction mixture of its other products
       • Some of the reactants may react in ways different to the expected reaction to give unexpected products.