rate and extent of chemical change

• Le Chatelier's Principle


  States that if a stress is applied to a system at equilibrium, the system shifts in the direction that relieves the stress.
• Define equilibrium


  Equilibrium is established when the rate of the forward reaction is equal to the rate of the reverse reaction.
• Define collision theory


  For a reaction to proceed, the reactant particles must collide with sufficient energy and appropriate orientation
• How do we measure rate

  By EITHER formation of product, or reactants being lost
• Define rate of reaction

  The amount of collisions of a substance (multiple) per second
• Define exothermic


  A chemical reaction that releases energy
• define endothermic


  A chemical reaction that absorbs energy
• Define bond energy


  the energy required to break one mole of a particular covalent bond
• Avogadro's number


  6.02 x 10^23
• From a table, how do you calculate when a reaction is exothermic or endothermic? (4)

  - You calculate the total energy required to break the reactants down H2 breaks to H - H)

  - you calculate the energy required to form the product

  - energy required to break minus the energy required to form

  - if negative, its exothermic, if positive its endothermic
• The four factors that affect the rate of chemical reactions

  - Temperature

  - Catalyst

  - Concentration/Pressure

  - Surface Area
• What two things will a rate of a reaction at a particular point

  - Amount of energy the particles have; more energy can transfer during the collision

  - frequency of collisions; how often the particles collide and how successful they are.
• The more often particles collide

  the higher chance of successful collision and therefore faster reaction
• What happens to a reaction when when the temperature increases

  - particles gain more energy

  - move faster

  - collide more frequently

  - collide with more energy

  - more likely to exceed activation energy
• define concentration


  The amount of particles in a particular area
• Why does surface area affect the rate of a reaction?

  there is more area for particle collisions
• Why do catalysts increase the rate of reaction?

  they decrease the activation energy
• Define catalyst


  substance that speeds up the rate of a chemical reaction
• Define reversible reaction


  a chemical reaction in which the products re-form the original reactants
• Define equillibrium


  Steady state / balanced
• If a reaction requires heat to move from the products to reactants, what type of reaction is it?

  Endothermic
• If a reaction requires heat to move to the products from reactants, what type of reaction is it?

  exothermic
• Position of equilibrium depends on

  temperature, pressure, concentration