Rate Graphs

• Rate Graphs:

  • It is important you can interpret rate of reaction graphs 
  • Over the course of a reaction, the concentration of product will increase and the concentration of reactant will decrease (as it is being used up) as demonstrated below: 
• Rate of reaction graphs:

  
• • Rate of reaction graphs are also useful for calculating:
  • the mean rate of a reaction
  • the rate of reaction at a specific point
  • the time at which a reaction reaches completion 
  • In this case the graph shows
  • time on the x-axis 
  • volume of product formed or amount of reactant used up on the y-axis 
• Calculating the Mean Rate of Reaction :

  • To find the mean rate of reaction for the whole reaction then you calculate the overall change in the quantity described on the y-axis (e.g. volume of gas produced or reactant used up) and divide it by the total time taken for the reaction 
  • You can also find the mean rate of reaction between any two points in time by calculating the change in of the reactant or product occurring in that time frame, and dividing it by the section of time being studied
• Calculating the Rate of Reaction at a Particular Point:

  • To do this you need to find the gradient of the curve at that point
  • To do this a tangent is drawn to the curve and then the gradient of the tangent calculated 
• Using Reaction Times:

  • The reaction time is the total time taken for the reaction to happen
  • The rate of reaction is inversely proportional to the reaction time, so as the reaction time increases the rate of reaction decreases 
  • This means that 1 / time is directly proportional to the rate of reaction:

  1 / time = rate of reaction

  • Instead of plotting reaction time against your independent variable (temperature, concentration) the reaction times from the investigation can be converted to rates of reaction using 1/t and plotted instead to observe trends