The activation energy, Eₐ, of the reaction between aqueous manganate(VII) ions, MnO₄⁻(aq), and aqueous ethanedioate ions, C₂O₄²⁻(aq), can be determined as follows. step 1 Use a pipette to transfer 10.00 cm³ of 0.0200 mol dm⁻³ MnO₄⁻(aq) into a boiling tube. step 2 Use a second pipette to transfer 10.00 cm³ of 0.0500 moldm⁻³ C₂O₄²⁻(aq) into a second boiling tube. step 3 Place both boiling tubes into a water-bath at approximately 50 °C and allow the temperature of both solutions to become equal and constant. step 4 Record this constant temperature. step 5 Pour the C₂O₄²⁻(aq) solution into the boiling tube containing the MnO₄⁻(aq) solution and immediately start the timer. Continue to stir the mixture during the reaction. step 6 When the reaction finishes, stop the timer and record the time. step 7 Repeat the experiment at different temperatures and record the results. The student used their recorded data to complete columns 1–3 of the table. experiment number | average temperature of reaction mixture (T) /K | time (t)/s | 1/T /K⁻¹ | log t ---|---|---|---|--- 1 | 333 | 11 | | 2 | 323 | 35 | | 3 | 315 | 76 | | 4 | 310 | 145 | | 5 | 304 | 284 | |

1. (a)An extra procedural step in the method is required in order to be able to calculate the average temperature of the reaction mixture throughout each experiment. State the extra procedural step that needs to be done.[1]
2. (b)Complete the empty columns in the table, giving all values to three significant figures.[2]
3. (c)Suggest why an experiment with an average temperature of 70°C (343K) would produce a result that is less accurate than the other experiments.[1]
4. (d)Identify the dependent variable.[1]
5. (e)Plot a graph on the grid to show the relationship between log t and 1/T. Use a cross (x) to plot each data point. Draw a line of best fit.[2]
6. (f)(i)The equation for the line of best fit is shown. log t = Eₐ / (2.303 RT) + constant R = 8.314 J mol⁻¹ K⁻¹ Use your graph to determine the gradient of the line of best fit. State the coordinates of both points you used in your calculation. These must be selected from your line of best fit. Give the gradient to three significant figures. coordinates 1 .............................................................. coordinates 2 .............................................................. gradient = ...................................... K[2]
7. (f)(ii)Determine the activation energy, Eₐ, of this reaction. Give your answer to three significant figures. Include units. Eₐ = ...................................... units = ......................................[2]

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