Chemistry C3

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  • Chemistry C3
    • History of the Periodic table
      • Newlands
        • Law of Octaves
          • Noticed eighth element had similar properties so grouped them together
      • Mendeleev
        • Put elements in increasing atomic mass but moved some around and grouped them in similar properties leaving gaps where the pattern was disrupted
          • First version of the "modern" periodic table
        • These gaps were useful as they predicted the new element's properties.
      • Pre-Table
        • 1800s they went on atomic mass
        • These attempts included incorrect elements such as light
      • Modern Periodic table
        • The discovery of sub-atomic atoms meant that the modern table was in increasing atomic number
        • Can be used by scientists to predict new element's properties based on their atomic number and position
    • Group 1 and 7
      • Group 1- Alkali metals
        • The further you go down the table, the more reactive it becomes
        • they have similar properties due to the 1 electron in the outermost shell
        • reacts with water to make a salt and hydrogen E.G sodium + water makes sodium hydroxide and hydrogen gas
      • Group 7 - Halogens
        • The further down  you go, the less reactive they are
        • The more reactive halogens will displace the less reactive ones.
      • React together violently to make ionic compounds
    • Transition metals
      • "Normal" metal properties
        • Good Conductors
        • Very dense, strong and shiny
        • Less reactive than group 1 alkali metals
        • very high melting point (excluding mercury)
      • Compounds
        • very colourful
          • Fe2+ is green, Fe 3+ is brown, Potassium Chromate is yellow, Potassium Manganate is purple, Copper sulphate is blue, Copper is green
        • good catalysts
    • Water
      • Hardness
        • Permenant
          • Caused by calcium sulphate ion amongst others
        • Temporary
          • Caused by the hydrogencarb-onate ion
          • Treatment
            • Permenant
              • Caused by calcium sulphate ion amongst others
            • Temporary hardness can be removed by boiling which breaks the hydrogencarb-onate ion into hydrogen and carbonate
            • Both can be softened by adding washing soda (sodium carbonate)
            • Both can softened by using an ion exchange column
        • Treatment
          • Temporary hardness can be removed by boiling which breaks the hydrogencarb-onate ion into hydrogen and carbonate
          • Both can be softened by adding washing soda (sodium carbonate)
          • Both can softened by using an ion exchange column
      • Treatment
        • 1. Water passes through mesh screen which removes big "bits"
        • 2. Chemicals are added to make microbes stick together and fall to the bottom
        • 3. The water is filtered though gravel beds to remove all solids
        • 4. Water is chlorinated to kill off any harmful microbes left
    • Reversible reactions
      • Equilibrium
        • Changed by: pressure and temperature
        • Means that the amounts of reactants and products will reach a certain balance and stay there
        • Catalysts just speed up the reaction they don't change the position of equilibrium
      • Haber process
        • Higher pressure favours the production of ammonioa
          • Because a high pressure is dangerous and expensive, A set pressure of 200 atmospheres is used.
        • Higher temperature doesn't favour the production of ammonia but the temperature is high to speed up the rate of reaction
          • Compromise
            • Because a high pressure is dangerous and expensive, A set pressure of 200 atmospheres is used.
    • Organic Chemistry
      • Alcohols
        • Has an OH functional group
        • General formulae is CnH2n+1OH
        • Uses: As a solvent, esterification, A fuel and in alcoholic drinks
      • Carboxylic Acids
        • Has the functional group COOH
        • They react like any other acid.  However, they don't dissociate very well in water (separate) as this reaction is reversible. This means that for an acid they have a relatively high PH.
        • Named after the alcohol that has been oxidised with the term "-anoic acid"
      • Esters
        • Has the functional group COO-
        • They are formed by mixing an alcohol with an carboxylic acid in the presence of a strong acidic catalyst. The name comes from the alcohol first with the ter Xthyl. the second part is the carboxylic acid with the term Y-anoate. The X compound is the alcohol and the Y was the Carboxylic acid.
        • Uses: Flavourings, Perfumes (As they are volatile) and some are used as solvents.

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