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Physical chemistry - Coggle Diagram

- - - - Lattice enthalpy can be defined in 2 ways , these are lattice enthalpy of formation and lattice enthalpy of disassociation.
        
        Lattice enthlapy of formation
        
        Lattice enthlay of formation is the energy change form when one mole of a perfect crystal is formed form its gaseous ions.
        
        A single bond making is not the entire lattice enthalpy of formation. the lattice enthalpy of formation is the total energy needed to form one mole of perfect lattice form its gaseous ions.
        
        Lattice enthalpy of formation and disassociation are complete opposites of each other. this means that if you reverse the sign in front of the enthalpy , then you also reverse the type of enthalpy.
        
        Lattice enthalpy of disassociation is defined as the enthalpy change when one mole of a crystal disassociates into its gaseous ions.
        
        For a perfect crystal , the lattice enthalpy of disassociation would be the energy needed to break down one mole of the entire lattice structure.
    - - The lattice enthalpy of formation is the enthalpy change when one mole of a substance is produced from its elements under its standard state.
        
        the enthalpy of formation of carbon dioxide would require carbon and oxygen atoms all in their gaseous phase and under their standard states , meaning diatomic for oxygen.
        
        A lot of steps occur within the process of the lattice of formation , this is known as the born-harber cycle.
        
        The enthalpy of formation is the sum of all of the formations together of all the endothermic reactions + the exothermic reactions.
    - - Ionisation energy is defined as the energy change when one mole of gaseous atom loses mole of electrons to form one mole of gaseous ions under standard conditions.
    - - The enthalpy of atomisation is defined as the enthalpy change when one mole gaseous atoms is formed from the elements in its standard states.
    - - Bond enthalpy is defined as the average enthalpy change when one formation of a ole of identical bonds in the gas phase.
        
        exam warning
        
        with examples like methane , the average bond enthalpy is not always constant. this is as you remove a hydrogen , the bonding pairs are more attracted towards the carbon and so the bond becomes much more stronger. this means that the carbon-hydrogen bond increases.
        
        Sometimes , the experimental value and theoretical values are different. this is because the experimental value has been found through experiments whilst the theoretical value which implies perfect conditions. Theoretical bond enthalpies are used in theoretical whilst average bond enthlapies are used in
      - It is also defined as the average chemical energy store within the bond after formation.
    - - Electron affinity is defined as the enthalpy change when one mole of an electron is added to one mole of gaseous atom to form one mole of gaseous ions.
    - - Born-Harber cycles are used to calculate some of of the types of bond enthlapies form experimental data
      - Born-harber cycles are used to break down n ionic reaction into a series of steps.
      - the harber process can be broken down into a few steps. the pure element is turned into a gaseous atoms , then the ions are formed via electron affinity and ionisation , then the gaseous ions condense into a crystal , then this is used to generate a harberprocess.
      - lattice enthlapy calculaton
        
        To calculate the lattice enthalpy from a born-harbor cycle , you treat it as if it is like one large Hess cycle.
        
        One route is representative of the products of enthalpy of formaton.
        
        Knowing what a born-harber cycle looks like is really important as it allows for rearrangement.
        
        The other route taken is the sum of every other enthalpy change.
        
        You can rearrange the it to find out the lattice enthalpy.
      - Sometimes there exists theoretical differences
        
        The calculated lattice enthalpies are close but not prefect. this is because the theoretical model uses the ionic model which posits that ions are perfect spheres nd have an equal distribution of charge.
        
        Ions have some level of covenant bonding within them. this casues some theroetical difference.
      - Polarisation occurs when positive ions are said to polarize negative ions. this causes a distortion in the charge cloud on one side of the ion.
        
        There is a spectrum between ionic and covalent bonding
        
        If lattice enthalpy is calculated , then it is very different from the experimental value and this is down to the large degree of covenant character present.
        
        If the theoretical value is close to the experimental value , then it means that there is very little covalent character.
    - - Enthalpy of hydration
        
        The enthalpy of hydration is defied as the enthalpy change when one mole of gaseous ions dissolve from one mole of aqueous ions.
        
        The enthalpy of solution defied as the enthalpy change when one mole of a solid crystal dissolves in large excess of solvent.
        
        Enthalpy of solution is defined as the enthlapy pf hydration + enthalpy of disassociation.
  - - - enthalpy change as defined as heat change under constant pressure is not enough to determine whether a reaction has occured.
      - When sodium chloride dissolves , the reaction is endothermic (meaning bond making) although energy is required
      - Solubility is the measurement of disorder. substances are always more stable when they have more disorder present.
        
        Substances are more soluble in water as they have a greater disorder.
        
        This is because everything tends to increase increase in disorder.
        
        An example is the reason why your phone cable gets tangled in your pocket and why sodium chloride dissolves in water , even though as its entropy increases.
      - Entropy is defined as the number of ways molecules ca be arranged.
        
        Entropy is a measure of disorder and increases within a reaction. the more disordered the atom
        
        The more entropy present in a reaction , the faster the reaction will occur as more ions have a greater possibility for collisions.
    - - Entropy is affected by a temperature increase as the speed of the particles move at. this increases the disorder and so increases entropy.
        
        when they are moving faster , the particles are more likely to be disorganised and so entropy increases.
        
        for a reaction to occur , activation energy is needed and also stoichiochemistry - the molecules have to be in the right rotation/arrangement.
      - Entropy is also affected by the physical state. this is as the molecules in a gas move at a faster speed. this means that they will have a higher entropy than solids and liquids.
        
        solids have less entropy than liquids which have less entropy than gasses.
      - Entropy is also affected by the number of molecules present as having less moles means that there is less molecules for collisions which results in less entropy.
        
        Increasing the number of moles increases entropy as there are more particles as there are more ways in which the particles can be disordered and so entropy increases as a result.
    - - A reaction is more likely to happen if the reaction increase the moles of a substance, gas is produced and the solid is consumed , the reaction is exothermic.
        
        if a reaction is exothermic ,then we are increasing the temperature and this increases the disorder.
        
        if a solid is consumed to produce gas , you are going from one state of matter which has a low state of entropy to a higher state of matter which has a higher state of entropy
        
        The more moles allows for the different combinations of how molecules react together.
    - - Standard entropies were developed over time and contain the measurement of hundreds of molecules and elements which have been measured under standard pressure and standard temperature
        
        Standard temperature = 298k and standard pressure = 1atm pressure