The reaction between solution EE and FF is represented by the following equation: $$S_2O_8^{2-}(aq) + 2I^-(aq) \rightarrow 2SO_4^{2-}(aq) + I_2(aq)$$ This reaction is followed by the reaction of iodine (I2) with the thiosulphate ions ($S_2O_3^{2-}$) provided in the mixture: $$I_2(aq) + 2S_2O_3^{2-}(aq) \rightarrow 2I^-(aq) + S_4O_6^{2-}(aq)$$ Initially the solution is clear but as the reaction proceeds, the concentration of iodine increases and the solution starts to become cloudy. The rate of reaction is measured by timing how long it takes for the cross to disappear completely when viewed from above. (ii) Prepare a water bath using 250 cm3 or a 300 cm3 beaker. (iii) Measure exacctly 10 cm3 of solution FF and 10 cm3 of EE and pour into separate boiling test tubes. (iv) Put the two boiling test tubes into the water bath in step (ii) and warm the contents to 40oC. (v) Pour the hot solutions FF and EE into the 50 cm3 beaker in step (i) and immediately start the stopwatch/clock. Record the time taken in seconds for the cross to disappear completely. (vi) Repeat the procedures stated in (iii) to (v) at different temperatures of 50oC, 60oC and 70oC and record your readings as shown in the following table.

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Determine the effect of temperature on the rate of chemical reaction. Study the reaction between sodium thiosulphate and hydrochloric acid. The chemicals provided are labeled as FF, containing 0.2 M sodium thiosulphate solution and EE, containing 0.1 M hydrochloric acid solution.You are also provided with thermometer, stopwatch/ stop clock and a sheet of white paper marked X. Proceed as follows: (i) Place 50 cm3 beaker on top of cross X on the plain sheet of paper provided such that the cross X is visible through the mouth of the beaker

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