Please enable JavaScript.

Coggle requires JavaScript to display documents.

Chapters 11 & 12 (Enthalpy Change (Communicating Enthalpy CHanges…

- - - - Isolated systems are systems where neither matter nor energy can be transferred between itself and its environment. This is necessary in calorimetry to determine precise quantities of transferred energy.
      - Thermal Energy
        
        Calculates the amount of thermal energy transferred in Joules or kiloJoules
        
        Formula: Q = mcΔt
        Where: Q is the quantity of thermal energy transferred
        m is the mass of the substance
        c is the specific heat capacity of the substance
        and Δt is the change in temperatur
      - Specific heat capacities
        
        A specific heat capacity is the amount of energy needed to change the temperature of 1 gram of a substance by 1 degrees Celcius.
        
        The specific heat capacity of water (it is also used as a constant for substances with no determined specific heat capacity) is 4.19 J per g°C
      - Calorimetry examples & bomb calorimetry http://www.physicsclassroom.com/class/thermalP/Lesson-2/Calorimeters-and-Calorimetry
  - - - Reference molar enthalpy: enthalpy of equation set at zero to compare other reactions
  - - - Molar enthalpy of oxidation of ammonia (ΔoHm) is -905.2kJ / 4 = -226.3 kJ/ mol NH4
    - - 4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g) ΔH = -905.2 kJ
      - Negative value is exothermic, positive value is endothermic
    - - Endothermic: heat/energy is a reactant Exothermic: heat/energy is a product
      - 4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g) + 905.2 kJ.
    - - High-Low, Exo!
      - Endothermic: positive 'slope' Exothermic: negative 'slope'
      - http://www.docbrown.info/page03/3_51energyB.htm
  - - - Smaller equations that appear in a larger equation can be used to determine the enthalpy of a more complex equation.
        ΔrH= ΔH1 + ΔH2 + ΔH3....
        
        https://www.chemteam.info/Thermochem/HessLawIntro1a.html
      - We can use this easier equation to do the same thing:
        ΔH°rxn = Σ ΔH°f, products minus Σ ΔH°f, reactants
        
        https://www.chemteam.info/Thermochem/HessLawIntro1a.html
- - - - Catalysts provide an alternative pathway that requires less activation energy
      - Does not affect net enthalpy of a reaction
      - Enzymes are organic molecules (usually proteins) that catalyze biological reactions
  - - - Intermediates are entities formed at an in-between stage of a reaction. They are less stable than the product, and do not appear in the final product.
      - Activated Complexes are molecules formed from the collision of the reactants before becoming the products