Convert temperature to kelvin, calculate the required reciprocal or logarithmic terms, plot the stated linear form and use the signed gradient with R before converting to kJ mol⁻¹.
A group of students investigated the kinetics of a 'clock' reaction.
The reaction investigated was that between hydrogen peroxide and iodide ions in the presence of acid.
Reaction \(1 \quad \mathrm{H}_{2} \mathrm{O}_{2}(\mathrm{aq})+2 \mathrm{H}^{+}(\mathrm{aq})+2 \mathrm{I}^{-}(\mathrm{aq}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{I}_{2}(\mathrm{aq})\)
In this 'clock' reaction, a fixed volume of aqueous sodium thiosulfate, , and a small amount of starch were added to the reaction mixture.
The added thiosulfate ions react with the iodine produced in Reaction 1.
Reaction \(22 \mathrm{~S}_{2} \mathrm{O}_{3}^{2-}(\mathrm{aq})+\mathrm{I}_{2}(\mathrm{aq}) \rightarrow \mathrm{S}_{4} \mathrm{O}_{6}^{2-}(\mathrm{aq})+2 \mathrm{I}^{-}(\mathrm{aq})\)
When all the thiosulfate ions have reacted, the presence of iodine is detected by the formation of a starch-iodine complex. The students recorded the time taken for this complex to form.
The activation energy for Reaction 1 may be found by repeating the experiment at different temperatures.
Each student carried out an experiment at a different temperature.
One of the students misread the thermometer in their experiment.
The activation energy, , for a reaction may be found by plotting a graph of In rate against 1 / T.
The gradient of the resulting line of best fit can be used in the Arrhenius equation to determine a value for , in .
Determine the value for for Reaction 1 by plotting a graph using the axes provided.
You should take into account the error made by one of the students.
The students all used thermometers capable of reading to the same precision. Use your graph to deduce the temperature that the student who made the error should have read on their thermometer.
