C6-Rate and extent of chemical change

• what is the rate of a reaction?

  how fast the reactants are changed into products
• what is a slow reaction?

  rusting of iron
• what is a fast reaction?

  burning
• how can you find the speed of a reaction?

  amount of product formed or amount of reactant used up
• what do the quickest reactions show on a graph?

  steepest lines and become flat in the least time
• what does the rate of a chemical reaction depend on?

  -the frequency of collisions, the more collisions=faster reaction

  -the energy transferred during a collision to create successful collisions
• what is the minimum amount of energy that particles need to react?

  activation energy
• why do particles need activation energy?

  to break bonds
• what are 4 factors affecting the rate of reaction?

  -temperature

  -concentration and pressure

  -surface area

  -catalyst
• how does temperature increase rate?

  increased temperature=faster particles

  leads to more frequent collisions

  leads to more successful collisions
• how does concentration and pressure increase rate?

  more concentrated=more particles colliding in the same volume of water

  increased pressure=same number of particles occupies a smaller space=more frequent collisions
• how does surface area increase rate?

  breaking a solid into smaller pieces increases the SA:Vol

  so for the same volume of solid, the particles will have more area to work on=more frequent collisions
• how does a catalyst increase the rate?

  catalyst=a substance that speeds up a reaction without being used up

  they decrease activation energy by providing an alternative reaction pathway with a lower activation energy
• how to find mean reaction rate from a graph?

  change in y / change in x
• how to find the reaction rate from a particular time?

  draw a tangent at the time and find the gradient

  gradient=change in y / change in x
• what is a reversible reaction?

  when the forward and backward reactions occur at the same rate
• what is an equilibrium?

  when the forward and backward reactions happen at the same rate in a closed system
• what happens when the equilibrium lies to the right?

  concentration of the products is greater than the reactants
• what happens when the equilibrium lies to the left?

  concentration of reactants is greater than the products
• if the reaction is endothermic in one direction, the reaction is exothermic in the other
• what is Le Chatelier's principle?

  if you change the conditions of a reversible reaction at equilibrium the system will try to counteract the change
• what happens to a reaction if you decrease the temperature?

  -equilibrium moves in the exothermic direction to produce more heat

  -get more products for the exothermic reaction
• what happens to a reaction if you raise the temperature?

  -equilibrium moves to the endothermic direction to try and decrease it

  -more products for the endothermic reaction
• what happens to a reaction if you increase pressure?

  equilibrium moves to the side with fewer moles to reduce the pressure
• what happens to the reaction if you decrease pressure?

  equilibrium moves to the side with more moles to increase the pressure
• what happens to a reaction if you increase the concentration of reactants?

  makes more products to decrease the concentration of reactants
• what happens to the reaction if the concentration of products is decreased?

  reduces amount of reactants to increase concentration of products again