Gen Chem

• Endothermic process


  Process that absorbs heat from the surroundings
• Exothermic process


  Process that gives off heat to the surroundings
• Thermodynamics

  A scientific discipline that deals with the interconversion of heat and other forms of energy
• Enthalpy, H


  A thermodynamic quantity used to describe heat changes taking place at constant pressure
• Enthalpy difference

  Difference between the enthalpies of the products and the enthalpies of reactants
• Spontaneous process


  A physical or chemical change that occurs by itself. A process that takes place without energy from an external source
• Entropy, S


  A thermodynamic quantity that is a measure of how spread out or dispersed the energy of a system is among the different possible ways that system can contain energy
• Absolute Entropy


  The absolute value of entropy of a substance
• Standard entropy, S°


  The absolute entropy of a substance at 1 atm and 25 °C
• Gibbs Free Energy, G


  Energy available to do useful work. Used to express the spontaneity of a reaction more directly
• The First Law of Thermodynamics: "Energy of the universe is constant."
• The Law of Conservation of Energy: "Energy can be converted from one form to another but cannot be created or destroyed."
• Standard Free Energy, ΔG°


  The free energy change for reaction when it occurs under standard state conditions, when reactants in their standard states are converted into products in their standard states
• Equilibrium constant, K


  A number equal to the ratio of the equilibrium concentrations of the products to the equilibrium concentrations of reactants, each raised to the power of their stoichiometric coefficients
• State functions


  Properties that can be expressed as (final - initial) states
• For thermodynamic studies we need to divide the universe into two parts: the system (part we are investigating) and the surroundings (everything else)
• System Change is based on going from initial state to final state. It is and ALWAYS written System final - System initial and using the symbol Δ for change.
• Properties that can be expressed as (final - initial) and we write with Δ such as ΔE = Ef - Ei are called state functions.
• Properties that you cannot calculate by just knowing final and initial states but must know how process occurred are called path functions.
• The First Law of Thermodynamics: Energy of the universe is constant. Energy can be converted from one form to another but cannot be created or destroyed.
• The Second Law of Thermodynamics: Entropy of universe increases.
• The Third Law of Thermodynamics: At absolute zero, the entropy of a perfect crystal is zero.
• Spontaneous process


  A physical or chemical change that occurs by itself. These processes occur without requiring an outside force and continue until equilibrium is reached.
• Spontaneous processes


  • Heat flows from a hotter object to a colder one
  • An iron object rusts in moist air
  • Sugar dissolves in a cup of coffee
• A spontaneous process is one that takes place without energy from an external source. For a chemical reaction to be spontaneous, it should proceed as written (from left to right), without an input of energy.