Chemistry AS Revision

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  • Chemistry AS Revision
    • Module 4
      • Alkanes
        • Saturated - containing only single bonds
        • Aliphatic - containing carbon atoms joined in straight or branched chains
        • Naming Branched Alkanes
          • Identify which suffix to use
            • Identify the longest continuous chain of carbon atoms
              • Identify any side chains and which number carbon the side chains are on
                • Combine the suffix,stem and side chains to name the compound
                  • When two or more side chains are the same, use the prefixes di-, tri-. or tetra-
        • Trends in Boiling Points
          • Boiling point increases as the number of carbon increases
            • The amount of intermolecular forces between atoms increases
              • More thermal energy is needed to overcome these forces
                • So the boiling point increases
          • Boiling point decreases as the amount of branches increases
            • The amount of intermolecular forces decreases as they only operate over short distances
              • Less thermal energy is needed to overcome the forces
                • So the boiling point decreases
        • Reactions of Alkanes
          • Combustion
          • Incomplete Combustion
      • Alkenes
        • Reactions of Alkenes
          • Free Radical Substitution
            • Made up of 3 steps:
              • 2: Propagation - one free radical and one non-free radical
              • 1: Initiation - making free radicals via homolytic fission
                • Always using a diatomic halogen
              • 3: Termination - two free radicals adding together to form one non-free radical
                • Alkane with alkane
                • Halogen with halogen
                • Alkane with halogen
          • Addition
            • In an addition reaction, two reactants form one product
            • A molecule is added to the unsaturated alkene, breaking the double bond forming a single unsaturated compound
          • Substitution
            • In a substitution reaction,an atom or group of atoms is replaced by a different atom or groups  of atoms
          • Elimination
            • An elimination reaction involves the removal of a small molecule from a larger one
            • In an elimination reaction, one reactant molecule forms two products
        • Isomers - are molecules that have the same molecular formula but a different arrangement of atoms
          • Structural Isomer - the atoms are arranged in a completely different order
          • Chain Isomers - these isomers arise because  of the possibility of branching in carbon chains
          • Functional group Isomer - in this variety of structural isomerism, the isomers contain different functional groups i.e. ketone and aldehyde or carboxylic acid and ester
      • Haloalkanes
        • Hydrolysis of Haloalkanes
          • Chemical reaction involving water or aqueous solution of a hydroxide that causes the breaking of a bond in a molecule
          • In the hydrolysis of a haloalkane, the halogen atom is replaced by an -OH group
          • The rate of hydrolysis depends upon the strength of the carbon-halogen bond in the haloalkane i.e. C-F is the strongest
      • Alcohols
        • Elimination Reactions
          • Dehydration is any reaction in which a water molecule is removed from the starting molecule
            • an alcohol is heated under reflux in the presence of an acid catalyst such as concentrated sulfuric acid or phosphoric acid
        • Substitution Reactions
          • Alcohols react with hydrogen halides to form haloalkanes
            • When preparing a haloalkane, the alcohol is heated under reflux with sulfuric acid and a sodium halide
    • Module 2
      • Redox Reactions
        • A base neutralises an acid to form a salt - metal oxides, metal hydroxides, metal carbonates and ammonia are all considered bases
        • If the oxidation increases after the reaction, it has been oxidised
        • If the oxidation number decreases after the reaction, it has been reduced
      • Shells and Orbitals
        • Atomic Orbital - a region within an atom that can hold up to two electrons with opposite spins
        • Sub- Shell - a group of the same type of atomic orbitals within a shelll
          • s subshell - 2  electrons
          • p orbitals - 6 electrons
          • d orbital - 10 electrons
      • Shapes of Molecules
        • Linear - 180 / 2 bonded pairs
        • Trigonal Planar - 120 / 3 bonded pairs
        • Non - Linear -  104.5/ 2 bonded pairs / 2 lone pair
        • Tetrahedral - 109.5 / 4 bonded pairs
        • Octahedral - 90 / 6 bonded pairs
        • Pyramidal - 107 / 3 bonded pairs / 1 lone pair
      • Intermolecular Forces
        • Permanent dipole-dipole interactions
          • Basically polar bonds so H-Cl
        • Instantaneous / Induced dipol-dipole forces
          • The more electrons, the larger the induced dipole
          • the stronger the attractive forces between molecules
        • Hydrogen Bonds
          • Any bond between H-N , H-F or H-O
          • Hydrogen bonds hold water molecules apart in an open lattice structure
          • Solid ice is less dense than liquid water and floats

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