Amount of Substance

Amount of Substance

1. Mole

   • A large number of particles
     • 6.02x10^23 particles/ molecules / ions
       • Avogadro's Constant
       • number of particles = moles x avogadro constant
   • Moles = mass/mr
   • Moles = conc (moldm^-3) x vol (dm^3)
     • 1 dm^3 = 1000 cm^3
   • Ideal gas
     • pV = nRT
       • Tells you number of moles in a volume of gas
         • At room temp and pressure, one mole occupies the volume of 24dm^3

2. Atom Economy

   • Measure of the proportion of reactant atoms become desired product in a balanced equation
   • % A.E = (mr of product / sum of all reactant mr) * 100
   • High atom economy desired in industry
     • Better for environment - less waste
       • Waste costs money to remove safetly
     • High efficiency in using raw resources
     • Less money spent on seperating products and waste

3. Titrations

   • Used to find concentration of acid or akali solutions
     • Allows you to find out how much acid is needed to neutralise a akali and vice versa
       • Can use this data to work out conc of alkali/acid
         • Use a pipette to measure out volume of the solution oy want to know the conc of
           • Add few drops of indicator, then fill burette with standard solution of acid
             • Use funnel to pour acid into burette, doing it below eye level for safety
               • First do a rought tirtation to get a general idea of where the end point is
                 • Add the acid to the akali using burette with a regular swirl
                   • Then do an accurate titration by taking an initial reading to see exactly how much acid is in the burette
                     • Run the acid until within 2cm of then add dropwise, keep it accurate and not overshoot
                       • Work out the amount of acid used to neutralise the akali by final minus initial
   • Standard Solution
     • Standard solution is any solution you know the exact conc of
       • Standard Solution used in titrations
         • Do it by dissolving a known amount of solid in a known amount of water
           • Wieght solid and boat, subtract just boat to find precise mass of solid used
             • Add everything to volumetric flask and rinse beaker to make sure all solid in
               • Using a funnel to make sure all goes into flask, top up flask to line
                 • Add stopper and shake to make sure all mixed

4. Equations and Calculations

   • Writing ionic equations
     • Ionic substances in the equation will dissolve into ions
       • Cancel ions on both sides, reactants and products
         • Resulting in only reacting particles being shown
   • Using molar ratio
     • If you have 4 moles of reactant
       • Which forms 2 moles of product
         • 0.5 mol of reactant forms 0.25 moles of product

5. Types of Reactions

   • Compounds break down when heated, forming two or more products from one reactant
     • If solid reactant broken down, will only be pure if other products are gases
       • Thermal Decomposition

6. Percentage Yield

   • Yield is never 100%
     • Reactants lost
       • Reactants not fully reacted
   • % Yield = (Actual Yield / Theoretical Yield) * 100
     • Theoretical: mass of products that should be formed
       • Equal to the mass in mol=mass/mr
     • Actual: always less than theoretical

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