ENERGETICS

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  • ENERGETICS
    • Hess's law
      • The enthalpy change for a reaction is independant of the route
        • Provided the starting and final conditions and reactants an products are the same
      • Energy Cycles
        • ?H(3) = ?H(1) + ?H(2)
        • ?Hi,  first ionization energy
          • Eg: Li ion batteries
          • min. energy required to remove 1 mol of electrons from 1 mol of gaseous atoms
        • ?Hlat, lattice enthalpy
          • Eg: Amonium chloride, is part of the Solvay process used to produce sodium carbonate. It is formed by combining ammonia gas and hydrogen cloride gas.
          • ?H when 1 mol of a solid ionic compound is separated into gaseous ions under standard conditions
          • Born- Haber cycle
        • ?He, first electron affinity
          • Eg: the Cl ion is an essential electrolyte located in all body fluids responsible for maintaining acid/base balance.
          • ?H when 1 mol of gaseous electrons is added to one mol of gaseous atoms
    • Entropy & Spontaneity
    • Law of Conservation of Energy
      • Energy cannot be created or destroyed, only transformed from one form to another.
    • Enthalpy
      • Bond Enthalpy
        • Energy needed to break 1 mol of bonds in gaseous molecules under standard conditions
        • ?H = ?E (bonds broken) - ?E(bonds formed)
      • The heat  content of a system
        • A System is the area of interest
          • Open System
            • Can exchange energy and matter with the surroundings
            • Eg: The Earth
          • Closed System
            • Can exchange energy but not matter with the surroundings
            • Eg: closed cooler
          • The Surroundings are everything else in the universe
      • Enthalpy Change
        • Exothermic
          • Heat is given out by the system
          • Enthalpy of reaction is negative
          • Eg: Nuclear fission
        • Endothermic
          • Heat is absorbed by the system
          • Enthalpy of reaction positive
          • Eg: Photosynthesis
        • Standard Conditions
          • 100 kPa pressure
          • 1 mol  dm^-3  concentrationsfor all solutions
          • All substances in their standard states
        • q = m*c*?T
          • Specific Heat Capacity of Water is 4.18
          • Heat capacity is the heat needed to increase the temperature of an object by 1 K.
          • Assumptions being made
            • No heat loss from system
            • Water absorbs all heat
            • Water density is 1.00g cm^-3
        • Standard ?H  of formation
          • ?H when 1 mol of the substance is formed from its elements in their standard states under standard conditions
          • Eg: During the extraction of Fe in a blast furneace, the C(s) released is combined with Oxygen(g), forming Carbon Dioxide
          • ?H = sum of ?Hf(products) - sum of ?H  (reactants)
        • ?Hatom, Enthalpy of atomization
          • Eg: The reaction between Mg and sulfuric acid for the production of magnesium sulfate for medical purposes, H gas is produced.
          • ?H when 1 mol of gaseous atoms is formed from the element in its standard state.

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