Thermodynamics Part 2 Chemistry^3 Mindmap

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  • Created on: 19-12-22 13:42
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  • Thermodynamics - Part 2
    • Enthalpy and enthalpy changes
      • chemical systems can be classified as:
        • isolated systems = no exchange of energy or matter with the surroundings
        • open systems = both energy and matter exchange with the surroundings
        • closed systems = contain a fixed amount of matter but allow energy exchange
      • heat is energy transferred as a result of temp difference
      • work involves energy exchange as a result of motion against an opposing force
      • heat capacity relates the heat supplied to a substance to the resulting temp rise
      • Cp = molar heat capacity at constant pressure, Cv = molar heat capacity at constant volume
    • Enthalpy changes in chemical reactions
      • enthalpy change = heat transferred at constant pressure by a chemical reaction or process
      • standard enthalpy change of fusion = enthalpy change when 1 mol of substance melts at its MP and 1 bar pressure
      • standard enthalpy change of vaporization = enthalpy change when 1 mol of liquid vaporises at its BP and 1 bar pressure
      • standard enthalpy change of reaction = enthalpy change at 1 bar for a reaction with all components in their standard states [298.15K]
      • standard enthalpy change of formation = enthalpy change when 1 mol of substance is formed under standard conditions from its constituent elements in their standard states
      • hess's law = total enthalpy change for a chemical reaction is independent of the path by which the reaction occurs [starting and finishing states are same for each reaction path]
      • standard enthalpy change of combustion = enthalpy change when 1 mol of substance reacts completely with excess oxygen at 1 bar pressure
      • bond dissociation energy = enthalpy change per mole when a particular chemical bond is broken under standard conditions in the gas phase
      • mean bond enthalpy = mean value of bond dissociation enthalpy for the bond, averaged across a range of compounds
    • Internal energy and 1st law of TD
      • energy gained by a system = positive, energy lost by a system = negative
      • internal energy = sum of kinetic and potential energies of molecules in a sample
      • isothermal expansion of an ideal gas = change in internal energy = 0
    • Measuring energy changes
      • calorimeters can be calibrated by measuring the energy change for compounds with known enthalpy change of internal energy
      • solution calorimeters are used to study reactions that take place in solution


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