Kinetics too

• Hess's law
• Change of enthalpy in a chemical reaction


  Independent of the route by which the chemical change occurs
• Standard enthalpy of formation (ΔH°f)


  The heat change that results when one mole of a compound is formed from its constituent elements
• Standard enthalpy change of combustion (ΔH°c)

  The enthalpy change which occurs when one mole of the compound is burned completely in oxygen at STP
• Enthalpy change of solution (ΔH°son)

  The heat generated or absorbed when a certain amount of solute dissolves in a certain amount of solvent at STP
• Calculating standard enthalpy of a reaction (ΔH°rxn)

  Using Hess's law, ΔH°rxn = Σ(ΔH° products) - Σ(ΔH° reactants)
• Entropy


  The measurement of disorder of a system, given the symbol S, and it is temperature dependent
• Entropy trends


  • Entropy increases with dispersal of particles
  • Entropies of gases are larger than liquids and liquids are larger than solids
  • Entropies are greater for more complex molecules
  • Entropy increases with increased temperature
  • Entropy increases for increased volume
• Calculating change in entropy (ΔS)

  ΔS = Σ(S° products) - Σ(S° reactants)
• If ΔS is positive


  Entropy increases
• If ΔS is negative


  Entropy decreases
• Exothermic reaction


  A chemical reaction that releases heat into the surroundings. In this type of reaction, the change of enthalpy is negative (ΔH < 0).
• Endothermic reaction


  A chemical reaction that absorbs heat from the surroundings. In this type of reaction, the change of enthalpy is positive (ΔH > 0).
• Change of enthalpy (ΔH)


  The difference in enthalpy between the final and initial states of a system. It is a measure of the heat absorbed or released during a chemical reaction at constant pressure.
• Enthalpy (H)


  A thermodynamic property that measures the total heat content of a system. It is defined as the sum of the system's internal energy and the product of its pressure and volume.