Chapter 18 - Reaction Orders

Front 1

What is the order of reaction?

Back 1

The order of reaction with respect to a particular reactant tells you how the concentration affects the rate.

Front 2

What are orders 0, 1 and 2?

Back 2

• If you double the reactant's concentration and the rate stays the same, the order with respect to that reactant is 0.
  
• If you double the reactant's concentration and the rate doubles, the order with respect to that reactant is 1.
  
• If you double the reactant's concentration and the rate quadruples, the order is 2.
  

Front 3

What is the overall order?

Back 3

The overall order is the sum of the orders of all different reactants.

Front 4

How do you work out the order of a particular reactant?

Back 4

• You have to use experimental data.
  
• Continuously monitor the change in concentration of the reactant against time to construct a rate-concentration graph.
  
• Use an initial rates method to find out how the initial rate varies as you change the concentration of that reactant.
  

Front 5

How do you use a concentration-time graph to construct a rate-concentration graph to then use to work out the order of a reaction?

Back 5

Find the gradient at various points along the concentration-time graph.

Plot these points and then join them up with a line or smooth curve.

Front 6

What does the shape of the line of a rate-concentration graph tell you about the order?

Back 6

1. A horizontal line means changing the concentration doesn't change the rate, so the order is 0.
   
2. A straight line through the origin shows the rate is proportional to concentration and therefore the order is 1.
   
3. If the line is curved, the order is 2. The rate is proportional to rate^2