Investigating the Kinetics of the reaction between Iodide ions and Peroxodisulphate (VI) ions (entire plan)

PLANNING

Investigating the Kinetics of the reaction between Iodide ions and Peroxodisulphate (VI) ions

By the use of an Iodine clock reaction I hope to obtain the length of time taken for Iodine ions (in potassium iodide) to react fully with Peroxodisulphate ions (in potassium Peroxodisulphate). I will do three sets of experiments changing first the concentration of iodide ions, then the concentration of Peroxodisulphate ions and finally the temperature of the solution in which the reaction is taking place. From these results, I hope to draw conclusions as to the effects of these changes to the environment of the reaction on the rate and also determine the order of the reaction and the activation enthalpy.

Background information

The rate of a reaction is determined by a number of factors. These include: pressure, temperature, concentration of reactants, surface area of reactants, presence of a catalyst and radiation.

The effect of these factors can be explained using collision theory. Reactions occur when the reactant particles collide, provided the colliding particles have enough energy for the reaction to take place. As the molecules approach their electron clouds repel. This requires energy – the minimum amount of which is called the ‘activation enthalpy’ - and comes from translational, vibrational, and rotational energy of each molecule. If there is enough energy available, this repulsion is overcome and the molecules get close enough for attractions between the molecules to cause a rearrangement of bonds and therefore an ‘effective’ reaction has taken place. The more collisions of particles with kinetic energy over the activation enthalpy that occur, the faster the overall reaction. During this investigation I am focusing on the effect of temperature and concentration while aiming to maintain other rate determining factors at a constant level in order to ensure reliable results.

Effect of concentration

Taking the collision theory into account the effect of concentration is simple in that the more particles of the reactants there are in the same area of space the more likely the collisions and therefore the faster the overall reaction. The following equation has been determined through experimentation showing that the rate of a reaction depends on concentration of reactants A:

Rate [A]n

Where n is a constant called the order of the reaction. T...

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... record the temperatures of every experiment and take into consideration how this may affect the results. Also, it is important to record the start and end tempertaure of the solution during the temperature-focused experiments because higher temperature lose their heat more quickly and if the temperature drops during the time of the reactions this information has to be involved in finding the average temperature.

Predications

I predict that the higher the concentration of the reactants the higher the rate of the reaction.

I predict that the higher the temperature of the reactants the higher the rate of the reaction.

I predict that the order of the reaction with respect to I- ions will be 1 and the order of the reaction with repect to S2O82-ions will also be 1 giving a overall order for the reaction of 2. This is information obtained from data books and backed up by information from the internet. (see references)

I predict that the activation energy of the reaction will be 52.9 kJ mol-1. This information is taken from the ILPAC Resource Pack for Advanced Practical Chemistry and is for the uncatalysed reaction between iodide ions and peroxodisulphate ions.