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Reaction Rate Graph Tutorial 3

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Reaction Rate Graph Tutorial 3

  1. 1. <ul><li>Instructions: </li></ul><ul><li>Use this slide show to consider some key questions about reaction rate graphs </li></ul><ul><li>Click on the next slide button to see the answers and an explanation about each question </li></ul>Understanding Reaction Rate Graphs
  2. 2. <ul><li>Which experiment shows the fastest reaction rate, a or b ? </li></ul>time (s) Volume gas / cm 3 b a 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22 11 5 10 15 20 25
  3. 3. <ul><li>Which experiment shows the fastest reaction rate, a or b ? </li></ul>time (s) Volume gas / cm 3 b a 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22 11 <ul><li>Answer… </li></ul><ul><li>Experiment ‘a’ </li></ul><ul><li>The gradient of experiment ‘a’ is always steeper than experiment ‘b’ </li></ul><ul><li>Compare the amount of gas produced after 2s </li></ul><ul><ul><li>experiment ‘a’ has produced 10cm 3 of gas </li></ul></ul><ul><ul><li>experiment ‘b’ has produced 15cm 3 of gas </li></ul></ul><ul><ul><li>… to produce more gas experiment a must be reacting faster </li></ul></ul>5 10 15 20 25
  4. 4. <ul><li>An experiment was run using the same reaction, but with different amounts of reactants. Which experiment used more reactants, b or c ? </li></ul>time (s) Volume gas / cm 3 b c 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22 11 5 10 15 20 25
  5. 5. <ul><li>An experiment was run using the same reaction, but with different amounts of reactants. Which experiment used more reactants, b or c ? </li></ul>time (s) Volume gas / cm 3 b c 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22 11 5 10 15 20 25 <ul><li>Answer… </li></ul><ul><li>Experiment ‘c’ </li></ul><ul><li>Remember, the reactants react to produce the products </li></ul><ul><li>The more reactant you put in, the more products will be formed </li></ul><ul><li>Experiment b eventually produced approximately 24cm 3 of gas, whereas experiment c produced 30cm 3 of gas </li></ul>
  6. 6. <ul><li>List two ways that you could compare the rates of these two reactions </li></ul>time (s) Volume gas / cm 3 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22 11 5 10 15 20 25 b a
  7. 7. <ul><li>List two ways that you could compare the rates of these two reactions </li></ul>time (s) Volume gas / cm 3 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22 11 5 10 15 20 25 b a <ul><li>Approach 1: Work out the rates by taking the gradients </li></ul><ul><li>The first part of a rate graph is always a straight line </li></ul><ul><li>The gradient of the line is equal to the reaction rate </li></ul><ul><li>To calculate the gradient you need to: </li></ul><ul><ul><li>pick a point on the straight part of the line </li></ul></ul><ul><ul><li>read the values for this point on the y (vertical) and x (horizontal) axes; </li></ul></ul><ul><ul><ul><li>in this case: y=10cm 3 and x=2s </li></ul></ul></ul><ul><ul><li>divide y by x, or in this case: Volume of gas </li></ul></ul><ul><ul><ul><ul><li> time </li></ul></ul></ul></ul><ul><li>compare the equation above with the one in the section ‘Measuring rates of reaction ’ above </li></ul><ul><li>you should notice when you calculate the gradient of the line, you are actually divided the change in product (gas) by the time taken, which is how you calculate a reaction rate!!! </li></ul>
  8. 8. <ul><li>List two ways that you could compare the rates of these two reactions </li></ul>time (s) Volume gas / cm 3 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22 11 5 10 15 20 25 b a <ul><li>Approach 2: Time how long is takes to produce a set amount of product </li></ul><ul><li>Before the line becomes flat, a reaction with a faster reaction rate will produce a set amount of product quicker </li></ul><ul><li>Pick an amount of product that is on the straight part of each graph </li></ul><ul><li>Then read the time is took each reaction to produce this set amount of product </li></ul><ul><li>The less time is took to produce this amount of product, the faster the reaction </li></ul><ul><li>Whilst this method does not give you an actual reaction rate, it is a valid way of comparing how fast different reactions are happening </li></ul>
  9. 9. time (s) Volume gas / cm 3 b a 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22 11 5 10 15 20 25 <ul><li>Which part of the reaction rate graph shows </li></ul><ul><ul><li>the reaction slowing down because the reactants are running out </li></ul></ul><ul><ul><li>the reaction having stopped </li></ul></ul><ul><ul><li>The reaction happening at the fastest rate </li></ul></ul>c
  10. 10. time (s) Volume gas / cm 3 b a 1 2 3 4 5 6 7 8 9 10 12 13 14 15 16 17 18 19 20 21 22 11 5 10 15 20 25 c <ul><li>Answers: </li></ul><ul><ul><li>‘ b’ shows the reaction slowing down – the gradient of the curve is getting less, so the reaction rate must be slowing down </li></ul></ul><ul><ul><li>‘ c’ shows the reaction having stopped. No more products are being formed – the amount of gas is staying the same </li></ul></ul><ul><ul><li>‘ a’ show the reaction happening at the fastest rate. The gradient is the steepest at this point </li></ul></ul><ul><li>Which part of the reaction rate graph shows </li></ul><ul><ul><li>the reaction slowing down because the reactants are running out </li></ul></ul><ul><ul><li>the reaction having stopped </li></ul></ul><ul><ul><li>The reaction happening at the fastest rate </li></ul></ul>

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