A student plans to study the rate of hydrolysis of 2-bromo-2-methylpropane. [Diagram showing reaction] As the concentration of 2-bromo-2-methylpropane decreases during the reaction, the concentration of hydrogen ions increases. The student plans the following method. Step 1 Place 100 cm³ of a mixture of propanone and water into a conical flask. Step 2 Heat the mixture to 35°C and maintain this temperature. Step 3 Add 1.00 cm³ of 2-bromo-2-methylpropane to the mixture and start timing. Step 4 After 1 minute, transfer a 10.00 cm³ sample of the reaction mixture into a conical flask containing ice and 4 drops of methyl orange indicator. Step 5 Immediately titrate the 10.00cm³ of the reaction mixture with 0.0200 mol dm⁻³ sodium hydroxide. Step 6 Repeat sampling and titrating at regular time intervals over a total time of 45 minutes. Step 7 Heat the reaction mixture to 50 °C, remove the final sample, and titrate this.

1. (a)(i)State the apparatus you would use to maintain the temperature of the reaction mixture.[1]
2. (a)(ii)Suggest why the experiment is carried out away from naked flames.[1]
3. (b)(i)State the pieces of equipment and their capacities that you would use to: measure 1.00 cm³ of 2-bromo-2-methylpropane in step 3[1]
4. (b)(ii)transfer a 10.00cm³ sample of the mixture in step 4.[1]
5. (c)Explain why the reaction mixture is transferred into a conical flask containing ice.[1]
6. (d)State the measured dependent variable for this experiment.[1]
7. (e)(i)The student recorded the results. Vfinal is the final titre volume, 47.25 cm³ in step 7. Complete [Table 2.1] by calculating the value of Vfinal – Vt. Record the values to 2 decimal places.[1]
8. (e)(ii)The titre, Vt, is proportional to the concentration of the hydrogen ions. State what Vfinal – Vt is proportional to.[1]
9. (e)(iii)Plot a graph on the grid 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.[2]
10. (e)(iv)Circle the point on the graph you consider to be most anomalous. Suggest one reason why this anomaly may have occurred during this experimental procedure.[2]
11. (e)(v)Use the graph to find two half-lives, t½, for this reaction. State the coordinates of both points you used in your calculations. first t½: coordinates .............................................. and .............................................. half-life = .............................................. s second t½: coordinates .............................................. and .............................................. half-life = .............................................. s[3]
12. (e)(vi)Use your answer to (e)(v) to state the order of the reaction with respect to 2-bromo-2-methylpropane. Explain your answer. (If you were unable to obtain an answer to (e)(v) you may use the values 1050s and 1045s for the half-lives. These are not the correct values.) order = .............................................. explanation[1]

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