GENCHEM2

• Chemical Kinetics - is the study of rates of chemical reactions and mechanisms by which they occur.
• Reaction rate - is change in concentration per unit time. Unit is M/s or mol/L-s.
• Rates are negative for reactants and positive quantities for products.
• Rate laws - are mathematical expressions that describe the relationship between the rate of a chemical reaction and the concentration of its reactants.
• Reaction Order - in a rate law describes the mathematical dependence of the rate on reactant concentrations.
• Spontaneous Process - any process which occurs without outside intervention.
• Non-spontaneous Process - any process which occurs with outside intervention . Needs energy to carry out the process.
• Reversible Process – one which can go back and forth between states along the same path.
• Spontaneous Process: ∆H<0 & ∆S>0

  Product Favored (K>1)
• Non-Spontaneous Process: ∆H>0 & ∆S<0 Reactant Favored (K<1)
• Entropy (S) - is a measure of the disorder of a system. It is a state function.
• Spontaneous reactions proceed to lower energy or higher entropy.
• State function – a property whose value does not depend on the path taken to reach that specific value.
• ∆S > 0 - randomness increases
• ∆S < 0 - order increases
• Physical State: Entropy (S) : Gas > Liquid > Solid
• Temperature: As temperature increases, entropy increases.
• Molecular size : Larger molecules have higher entropy.
• Forces between particles in a solid: Entropy of a solid is higher if there are weak forces between particles.
• Dissolution and Mixing: Entropy of solid increases when dissolved in solution.
• Second Law of Thermodynamics - States that the entropy of the universe Increases in a spontaneous process and remains unchanged in an equilibrium process. This law explains why spontaneous processes have a direction.
• In any spontaneous process, the entropy of the universe increases and never decreases.
• Entropy is not conserved: ΔS universe is increasing.
• For a reversible process: ΔS universe = 0.
• For a spontaneous process (i.e. irreversible): ΔS universe > 0.
• Gibb's Free Energy - For a spontaneous reaction, the entropy of the universe must increase.
• Reactions with large negative ΔH values are spontaneous.
• ∆G < 0 : forward reaction is spontaneous
• ∆G = 0 : reaction is at equilibrium / no reaction
• ∆G > 0 : forward reaction is not spontaneous
• For a reaction , the free energy of the reactants decreases to a minimum (equilibrium) and then increases to the free energy of the products.
• Factors needed for reaction to proceed:

  1. There must be collision.
  2. Proper orientation of molecules.
  3. There must have activation energy.
• Collision Theory - states that a reaction results when reactant molecules, which are properly oriented and have the appropriate energy, collide.
• Factors That Affect Reaction Rates:

  1. Physical State of the Reactants
  2. Concentration of Reactants
  3. Temperature
  4. Presence of a Catalyst