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)
- 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.
- The difference between the final temperature and the initial temperature became lower and lower as the initial temperature increased. That is, the rate of heat lost to surroundings became higher and higher. Therefore, it is not advisable to perform the experiment at high temperatures.
- Mole of phenol is constant. Therefore the mole of reactants that had reacted when the solution turned colorless is also a constant. Therefore, it is not necessary to know how far the reaction has proceeded at the point where the methyl red is decolorized.
- “1/t” can substitute “k” in the following equation:
k = A e-Ea/RT
because “k” is proportional to the rate of the reaction while the rate of the reaction is proportional to “1/t”. But in this case the value of “A” will change with respect to the “A” before substitution.
- A equation relating “k” and “1/T” can be derived:
ln k = ln A – Ea / RT
a graph of ln(1/time) against (1/temperature) is plotted:
By linear regression,
The constant term (i.e. the y-intercept) of the equation = 23.1014
The slope of the graph is –8533.962
Therefore,
– Ea / R = –8533.962
– Ea / 8.3 = -8533.962
The activation energy of the reaction is 70831.887 J
The equation relating “k” and “1/T” is:
ln k = 23.1014 – 8533.962 / T
- The greater the temperature, the higher the reaction rate. This is because the increase in temperature increase the proportion of the fast moving election in the molecules of reactants. Thus more particles have energy greater than the activation energy which gives rise to the rate of reaction. Besides that, increase in temperature increase the most probable speed of the particles of the reactants. This increase the frequency of collision between particles and thus increase the rate of reaction.
Conclusion
The activation energy of the reaction between Bromide ion and Bromate(V) ion in acid solution is 70831.887 J
Discussion
- During sucking of methyl orange, the dropper should not be put too deep inside the methyl orange solution, as the precipitate in the solution may also be sucked into dropper. The precipitate is red in color and will not change color during reaction.
- When the phenol solution and solution A is pipetted, two pipetted is used instead of one. One for phenol solution and the other one for solution A.