STM 006

• Around 1850, Rudolf Clausius and William Thomson (Lord Kelvin) stated that heat does not spontaneously flow from a colder to a hotter body.
• The laws of Thermodynamics describe the relationships between thermal energy, or heat, and other forms of energy, and how energy affects matter.
• The First Law of Thermodynamics states that energy cannot be created or destroyed; the total Quantity of energy in the universe stays the same.
• The Second Law of Thermodynamics is about the quality of energy.
• Second Law of Thermodynamics - states that as energy is transferred or transformed, more and more of it is wasted.
• Second Law of Thermodynamics - states that there is a natural tendency of any isolated system to degenerate into a more disordered state.
• Entropy - the degree of randomness in a substance.
• Solids have very ordered and have low entropy.
• Liquids and Aqueous Ions have more entropy because they have more freely, and gasses have an even larger amount of entropy.
• According to the Second Law of Thermodynamics, nature is always proceeding to a state of higher entropy.
• You can expect a positive or increase in entropy when solid reactants from liquid or gaseous products.
• You can expect a positive or increase in entropy when liquid reactants form gases.
• You can expect a positive or increase in entropy when many smaller particles coalesce into larger particles.
• You can expect a negative or decrease in entropy when gaseous or liquid reactants form solid products.
• You can expect a negative or decrease in entropy when gaseous reactants form liquid products.
• You can expect a negative or decrease in entropy when large molecules dissociate into smaller ones.
• You can expect a negative or decrease in entropy when there are more moles of gas in the products than there are in the reactants.
• You can expect a positive or increase in entropy when indicated by fewer product moles than reactant moles.
• The Enthalpy of a substance is a measure of its total energy, and its changes represent the heat transferred in chemical and physical processes.
• Entropy - the measure of the disorder present in given substance or system.
• Gibbs Free Energy - always decreases in spontaneous process.
• The change in Gibbs Free Energy is the maximum work that has a spontaneous process can perform. It is also the minimum work required to carry out a nonspontaneous process.
• The partial pressure of any gases involved in the reaction is 0.1 MPa.
• The concentrations of all aqueous solutions are 1M
• Measurements are also generally taken at a temperature of 25 °c.
• Endothermic absorbs heat.
• Exothermic releases heat.
• Endergonic - non-spontaneous.
• Exergonic - spontaneous.
• Gibbs Energy - the chemical potential that is minimized when a system reaches equilibrium at constant pressure and temperature.
• Entropy - the loss of energy available to do work.
• Another form of the second law of thermodynamics states that the total Entropy of a system either increases or remains constant; it never decreases.
• Entropy is zero in a reversible process; it increases in an irreversible process.
• Reversible Reaction - a chemical reaction where directions for products that in turn, react together to give the reactants back.
• Reversible Reaction - will reach an equilibrium point where the concentrations of the reactants and products will no longer change.
• Reversible Reaction - donated by a double arrow pointing both directions in a chemical equation.
• Irreversible Reaction - a chemical reaction that only can occur in one direction.
• Irreversible Reaction - in this reaction, the reactants can change to the products, but the products cannot change back to the reactants.
• It was believed that all chemical reactions are irreversible until 1803, when French chemist Claude Louis Berthollete introduced the concept of reversible reactions.
• Claude Louis Berthollete - he observed that sodium carbonate and calcium chloride react to yield calcium carbonate and sodium chloride; however, after observing sodium carbonate formation around the edges of salt lakes, he realized that large amount of salts in the evaporating water reacted with calcium carbonate to form sodium carbonate, indicating that the reverse reaction was occurring.