Redox Reactions Test

Introduction

For today's practical session, the aim was to find out if the different substances were oxidising or reducing agents. For this test, we used:

• Aqueous potassium manganate (VII) --> Used to test for reducing agent
• Aqueous potassium iodide --> Used to test for oxidising agent
• Dilute sulfuric acid
• Solids P and Q, and solutions R and S

Procedure

1. Prepare solutions of substances P and Q by transferring half a spatula of each substance in separate test tubes and dissolving half a test tube of distilled water. Divide the solutions of P and Q into two portions to be used for Test 1 and 2 respectively.
   
2. For Test 1, add 1cm^3 of dilute sulfuric acid to each solution. Then add KMnO4 solution.
• Test 1 is testing for the presence of reducing agents. A positive test will involve a change in colour of solution from purple to colourless.
3. For Test 2, add 1cm^3 of dilute sulfuric acid to each solution. Then add KI solution.
• Test 3 is testing for the presence of oxidising agents. A positive test will involve a change in colour of solution from colourless to brown.
4. Record your observations in a table as shown below.

Observations

Solution S, Test 2: Brown solution (left) from original colourless solution (right)

From left to right: Solution P test 1 and 2, Solution R test 1 and 2

Close up of dark brown solution when KI is added to solution P.

Close up of purple solution when KMnO4 was added to solution P.

It is important to first add your sulfuric acid, otherwise your results would look something like that.

Conclusions

P is an oxidising agent based on the results from test 2.

Q is a reducing agent based on the results from test 1.

R is unreactive based on the results from both tests.

S is disproportionated based on the results from both tests.