Electrolysis: Potassium Iodide (Solution)

Aim:

To find the oxidising and reducing agent in an aqueous solution of potassium iodide

Equipment:

1x U-tube
Phenolphthalein indicator
0.5 mol L⁻ Potassium Iodide Solution
About 15ml of distilled water
A power supply
2x carbon inhert electrodes
2x wires connecting power pack to carbon electrodes

Procedure:

1.       Collect all equipment needed and make create an observation and reaction table

2.       The diagram below shows the basis of the apparatus’ setup.

3.       Once the setup looks like the diagram below add a mix of 15 ml of potassium iodide and 15 ml of the distilled water

4.       Turn the power (6V supply should be enough)

5.       Once you see some reaction take place, add a few drops of the phenolphthalein indicator to check for any type of bases that may be in the solution

6.      

Record all results and observations.

Results:

Anode	Cathode
Solution around anode becomes yellowish/brown in colour.	Solution around cathode bubbles and is clear until Phenolphthalein indicator is added then solution becomes purple.

Redox:

2I⁻ _(aq) → I₂ _(aq) + 2e⁻   Oxidised
2H₂O _(l) + 2e⁻   → H₂ _(g) + 2OH⁻ _(aq) Reduced
2I⁻ _(aq) + 2H₂O (l) → I₂ _(aq) + H₂ _(g) + 2OH⁻ _(aq) Redox Equation

Discussion:

This experiment has shown and taught us a few lessons. First off we can see that water is a stronger oxidising agent than potassium. For this reason water reacts at the cathode instead of potassium, therefore forming hydrogen gas and hydroxide ions. To prove this we added a few drops of phenolphthalein indicator which resulted the solution to turn to purple colour at the cathode, in other words meaning hydroxide ions as the phenolphthalein turns purple when it comes in contact with a basic solution and colourless with an acidic solution.

The anode has a very different story as the water is not a stronger reductant than iodine, therefore, we can say that iodine reacts at the ₂ is formed at the anode however our group could not confirm this to be Iodine gas as the solution turned brownish/yellow, and the WACE WA data sheet stated that I₂ in an aqueous solution turns to a brownish/yellow colour. Therefore, this would mean that the I₂ is actually an ion.

anode instead of the water. We can see that I

Our experiment resulted in near perfect results it was conducted more than once and all steps being performed as perfectly possible.

To conclude, we can see that water is a stronger oxidising agent compared to potassium, however it is a weaker reducing agent compared to iodine