Rate

• reactants --> products
• rate of reaction = speed of reaction (reactants into products)
• To measure rate =

  1. Measure speed that reactants decrease (are used up)
  2. Measure speed that products increase (are made)
• Rate of reaction = gradient (slope) of graph

  steeper the gradient = faster the reaction
• rate of reaction decreases with time (gradient gets less steep with time)
• Independent = variable you change
• mean rate = change/time (units = y/x)
• initial rate =gradient of tangent = vertical change/horizontal change (cm/s)
• rate at a certain time is in your book
• particles must collide with a certain amount of energy (Ea) in order for a reaction to occur
• greater no of successful collisions in a certain time = faster the rate
• To measure rate of reaction, we measure a change in either reactant or product in a given time
• 1. measure vol of gas given off in a certain time gas syringe to measure vol of H given off Benefits = scale is easily read; vols are recorded accuratley Con = syringe can stick; some gas is lost before bung is in place
• independent variable = variable that is changed
• dependent variable = variable that is measured
• when gradient reaches zero -> reaction has stopped
• rate is always fastest at the start -> greatest no. successful collisions
• as time goes on the product is used up -> less particles to collide with -> less successful collisions in a certain time -> rate decreaes
• no successful collisions = rate has stopped
• this is the graph for the reaction of a gas