Chemistry AS Revision
- Created by: hannahkrasner
- Created on: 23-01-19 10:32
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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-
- Combine the suffix,stem and side chains to name the compound
- Identify any side chains and which number carbon the side chains are on
- Identify the longest continuous chain of carbon atoms
- Identify which suffix to use
- 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
- More thermal energy is needed to overcome these forces
- The amount of intermolecular forces between atoms 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
- Less thermal energy is needed to overcome the forces
- The amount of intermolecular forces decreases as they only operate over short distances
- Boiling point increases as the number of carbon increases
- 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
- Made up of 3 steps:
- 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
- Free Radical Substitution
- 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
- Reactions of Alkenes
- 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
- Hydrolysis of Haloalkanes
- 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
- Dehydration is any reaction in which a water molecule is removed from the starting molecule
- 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
- Alcohols react with hydrogen halides to form haloalkanes
- Elimination Reactions
- Alkanes
- 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
- Permanent dipole-dipole interactions
- Redox Reactions
- Module 4
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