Propanone And Iodine Experiment

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The reaction between Propanone and iodine under acidic condition

Aims
To find the order of reaction with respect to propanone, iodine and sulfuric acid, thus proposing a rate equation.
Find rate constant at various temperature and with the use of the Arrhenius equation, find the activation enthalpy of the reaction.

General Method {For step by step guide of the experiment see preparation page}
By using known concentration of aqueous iodine solution (0.000 moldm-3, 0.005 mol dm-3, 0.015 moldm-3, 0.020 moldm-3, 0.025 moldm-3, 0.030 moldm-3, 0.035 moldm-3, 0.040 moldm-3, 0.045 moldm-3, 0.050 moldm-3, 0.055 moldm-3) and a colorimeter, find the absorbance for each of the concentrations. This can then be used to to plot a calibration curve (concentration
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This is because not all collisions are energetic collisions (are collision between molecules that has enough kinetic energy for reaction to take place) some does not have the required amount of kinetic energy to overcome the activation energy hence the reaction does not occur.

For this experiment the collisions that could occur between three reactants - (The diatomic iodine molecule, propanone (Acetone) and hydrogen ion (H+). The frequency of collisions are dependent on the number of particles of these reactants within a specific volume (moldm-3).

Collisions involving atoms, the orientation of them during collision determines whether the reaction would occur, without the proper orientations during the collision, the reaction will not occur at all and the molecules would bounce away. However even with the correct
Only the species with enough kinetic energy upon collision to overcome the activation enthalpy (repulsive energy barrier) will initiate a reaction and form products. If they collide with less energy than the Ea nothing happens and they bounce apart.

Ea is shown in the enthalpy profile of standard exothermic reaction. orientation between the species, they won’t react without the required activation
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To enable them to react we can either change the shape of the curve or move the activation energy (explain later on keep reading).

One of which is to increase the temperature of the reaction. As temperature increases the rate of reaction increases. This is because the particles becomes more energetic causing them to have more kinetic energy as a result they move faster and more collisions occur with the required Ea (collision frequency increases). Using this knowledge, to speed up a reaction, there needs to be an increase in the number of energetic particles (those with energies equal to or greater than the activation energy) and by increasing the temperature has that effect (changes the shape of the graph) as shown below.

Curve T: Original temperature
Curve T+t: At higher temperature

Comparing to our original curve (Figure 1.1, Curve T). Curve T+t shows the effect of temperature increase. More particles have the activation energy meaning more successful collisions occur which then leads to reaction, hence seeing the increase of the area under the Curve

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