The Rate & Extent of Chemical Change

• rates of reaction is measured by how much reactant or product produced in a certain time
• factors which affect the rate of chemical reactions:

  • concentration
  • pressure
  • surface area
  • temperature
  • catalysts
• when temperature increases, particles move faster so they will collide more easily
• more concentration means more particles
• more pressure means that particles occupy smaller spaces and have more frequent collisions
• breaking a reactant that is a solid into smaller pieces will increase surface area
• if particles have more space, there will be more collisions
• a catalyst is a substance that speeds up a reaction
• catalysts aren't used up in a reaction
• catalysts decrease the activation energy needed
• enzymes are biological catalysts
• collision theory states that chemical reactions can only occur when particles collide and if they have enough energy
• activation energy is the minimum amount of energy that particles need to react
• increasing the frequency of collisions increases the rate of reaction
• factors which increase collisions:

  • concentration
  • temperature
  • pressure
  • surface area
• catalysts are substances that speed up a reaction without being used up in the reaction
• catalysts increase the rate of reaction by providing a different pathway for the reaction with the lower activation energy
• reversible reactions is when products can react to produce their original reactions
• the direction of reversible reactions can be changed by changing the conditions
• an example of a reversible reaction:

  ammonium chloride ⇌ ammonia + hydrogen chloride
• if a reversible reaction is endothermic one direction, it will be exothermic at the other direction
• equilibrium is the point at which both rates of forward and backward reactions are the same

  the amount of reactants and products are the same
• the amount of the reactants and products at equilibrium depend on the conditions of the reaction
• La Chatelier states that if the conditions of a reversible reaction is changed, the system will respond to counteract that change
• if concentration of the reactant or product is changed, the reaction is no longer at equilibrium

  the concentrations will change until equilibrium is reached again
• an example of a reversible reaction:ammonium chloride ⇌ ammonia + hydrogen chloride
• if concentration of reactants is increased, more products will form until equilibrium is reached again
• if concentration of products decrease, the reactants will react until equilibrium is reached
• if there is an increase in pressure, equilibrium will try to reduce it by moving in the direction with fewer gas molecules
• if there is an decrease in pressure, equilibrium will try to increase it by moving in the direction with more gas molecules