Was going through some of my chem work today and there are some
observations which I do not understand why they were seen.
Say you have an unknown solid, G. You need to identify whether
it is an oxidising or reducing agent. Now, you are required to
SLOWLY add a few drops of either bromine water or iodine solution
to G in a test tube.
I added Br2,and later observed that a dark brown solution was
formed. According to what my teacher revealed later on, G is KI. So
I was wondering what would happen I was provided with Iodine
instead. There would be no reaction, isn't it? In this case, how do
I know whether unknown G (which is KI) is a reducing or oxidisng
agent?
Thank you.
If you add Br2 and a dark brown solution is formed.
It means that KI + Br2 ==> KBr + I2
Iodine being the dark brown solution formed.
This is your standard displacement reaction for Group 7.
In thise case since the oxidation no. of Br changes from 0 to
-1. It has been reduced. Which means that KI is a reducing
agent.
vice versa. the oxidation number of iodine changes from -1 to 0.
Hence it has been oxidised. Br2 acts as a oxidising agent.