My answer is concerned with qualitative testing for CuSO4 which is soluble in water producing copper(II) ions & sulfate ions in solution.
The sample, under testing, is placed in water & then divided into two halves.
The first half is tested by adding few drops of sodium hydroxide solution. Formation of blue precipitate is indicative of the presence of Cu2+.
To the second half, add few drops of aqueous solution of barium chloride. Formation of white precipitate indicates that it is barium sulfate implying the presence of SO42-.