To determine the activation energy of the reaction between Bromide ion and Bromate(V) ion in acid solution.

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Experiment 12

Aim:

To determine the activation energy of the reaction between Bromide ion and Bromate(V) ion in acid solution

Procedure

  1. 10.0cm3 of 0.01M phenol solution, 10.0 cm3 solution A (0.083M with respect to KBr and 0.017 M with respect to KBrO3) and 10 drops of methyl red indicator were placed into a boiling tube.
  2. 5.0 cm3 of 0.5M sulphuric(VI) acid was placed into a second boiling tube.
  3. Both boiling tubes were placed into a beaker of water which is maintained at about 30ºC. The contents of the tubes were allowed to reach the temperature of the water bath.
  4. The sulphuric(VI) acid was poured into the first boiling tube, and at the same time the stop watch was started. The boiling tube was swirled gently.
  5. The first boiling tube was kept in the water bath throughout the experiment. The time (t) taken was recorded, to the nearest second, for the complete disappearance of the red color.
  6. The temperature (T) of the reaction mixture at the end of the experiment was also recorded, to the nearest degree.
  7. Steps (1) to (6) was repeated, maintaining the reaction temperature at about 35ºC, 40ºC, 45ºC and 50ºC.
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Result

Calculation

Equation of the reaction between Bromide ion and Bromate(V) ion in Acid Solution:

5Br-(aq)+ BrO3-(aq) + 6H+(aq)  3Br2(aq) + 3H2O(l)

Equation of the reaction between phenol and bromine:

3Br2(aq) + C6H5OH(aq)  C6H2Br3OH(s) + 3H+(aq) + 3Br-(aq)

  1. Methyl red in this experiment was used as an indicator. At first, the solution was red purple due the present of methyl red. After all the phenol is consumed, any further bromine bleaches the indicator immediately. The solution then turned colorless.
  2. The difference between the final temperature and the initial temperature became lower and lower as the initial temperature increased. That is, the rate of ...

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