Answer:
Iodine testStep-by-step explanation:
Test tube B
The potassium iodide is added in excess to the solution of ferric sulphate to form ferrous sulphate ( here Ferric ions are getting converted into ferrous ions first) potassium sulphate and iodide. In this reaction , ferric sulphate is reduced to ferrous sulphate.
The reaction is as follows:
Fe2(SO4)3+2KI→2FeSO4+K2SO4+I2
In test tube A
We are adding potassium iodide directly in ferrous sulphate so no need of reduction it will immediately give iodine.