enthalpy

    Cards (17)

    • enthalpein (to warm)
    • enthalpy Represented by the symbol, H.
    • enthalpy refers
      to the energy transferred under constant pressure.
    • enthalpy Often referred to as the heat content
    • enthalpy cannot be measured but it is possible to measure the
      change in enthalpy or heat content, ΔH
    • Enthalpy change, ΔH, that accompanies chemical
      reaction is called heat of reaction.
    • enthalpy is the net energy change resulting from the breaking
      and making of bonds.
    • ΔH = Hproducts - Hreactants
    • The sign of ΔH indicates the direction of heat
      transfer.
      A positive value indicates that the system
      absorbs heat from the surroundings and is,
      endothermic.
      A negative value indicates that heat is released
      by the system, hence, the process is exothermic.
    • Enthalpy also indicates the amount of heat stored as
      potential energy.
    • in an exothermic reaction, the
      products will have a lower energy than the reactants.
    • A balanced equation in which the value of ΔH, with the
      appropriate sign, is usually written at the right side.
    • Balanced chemical equation:
      CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) + 890.4 kJ
      Thermochemical equation:
      CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) ΔH = −890.4kJ
      it is negative because heat is at the product side meaning the system produced heat meaning it is exothermic
    • Balanced chemical equation:
      CaCO3(s) + 177.8 kJ → CaO(s) + CO2(g)
      Thermochemical equation:
      CaCO3(s) → CaO(s) + CO2(g) ΔH = 177.8 kJ
      it is positive because the caco3 is heated resulting to the product meaning the substance is heated by the surrounding meaning it is endothermic
    • Calorimetry
      Concerned with the measurement of heat
      changes or heat flow in a chemical reaction.
      The device used to measure heat changes is
      a calorimeter.
    • hesss law states that ΔH = ΔH1 + ΔH2 +
    • hey
      hello
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