A scientist is asked to find the rate of decomposition of an aromatic diazonium compound and determine the order of the reaction with respect to the aromatic diazonium compound.

1. (a)The scientist is given 1.02g of an aromatic diazonium compound in a 50cm³ beaker. Describe the steps the scientist should take to make a 100.0cm³ standard solution containing 1.02 g of this compound. Give the name and capacity of the apparatus the scientist should use. Write your answer using a series of numbered steps.[3]
2. (b)(i)Benzenediazonium chloride, an aromatic diazonium compound, decomposes in solution to produce phenol and nitrogen gas. The scientist warms 50cm³ of the solution to 50°C. The scientist records the volume of nitrogen gas produced at different times during the decomposition. Identify the piece of apparatus that should be used to maintain the temperature of the solution.[1]
3. (b)(ii)Identify the dependent variable.[1]
4. (b)(iii)Suggest why the scientist does not monitor the reaction by measuring the loss in mass.[1]
5. (c)(i)Table 3.1 shows the results of the experiment. [Table 3.1] Vfinal is the final volume of nitrogen gas measured once the decomposition is complete. Vt is the volume collected at time = t. Vfinal − Vt is proportional to the concentration of the benzenediazonium chloride. Complete Table 3.1.[1]
6. (c)(ii)Plot a graph on the grid in [Figure 3.1] to show the relationship between Vfinal − Vt and time. Use a cross (x) to plot each data point. Draw a curved line of best fit through the plotted points.[2]
7. (c)(iii)Circle the one point on the graph that you consider to be most anomalous.[1]
8. (c)(iv)Suggest one reason to explain the anomalous point you have circled. Assume no error was made in the measurement of volume.[1]
9. (c)(v)Use your graph to find the first two successive half-lives, t₁/₂, for this reaction. State the coordinates of both points you used in each of your calculations. first t₁/₂: coordinates ............................................ and ............................................ half-life = ............................................ min second t₁/₂: coordinates ............................................ and ............................................ half-life = ............................................ min[2]
10. (c)(vi)Use your answer to (c)(v) to state the order of the reaction with respect to the benzenediazonium chloride. Explain your answer. If you were unable to obtain an answer to (c)(v) you may use the values 8.6 min and 11.0 min for the half-lives. These are not the correct values. order = .............................................. explanation ................................................................................................................................................................................................................................................................................................[1]

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