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Compound A
This is a white crystalline solid. The flame test gives a lilac flame. On treatment of a dilute solution of A with hydrogen peroxide solution a yellow colouration is seen. When hexane is added to the aqueous product and shaken it settles to give an upper purple layer.
The lilac flame test suggests a potassium salt. Hydrogen peroxide is an oxidizing agent. A yellow colour suggests the production of bromine or iodine. The purple layer with hexane indicates it is iodine. The original salt is therefore an iodide.
Answer: potassium iodide.
The iodine could also have been confirmed with a starch test. Alternatively, the iodide could have been identified with acidified silver nitrate solution. The pale yellow precipitate which formed would be insoluble in concentrated ammonia solution.