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Question:

Among PbS, CuS, HgS, MnS, Ag₂S, NiS, CoS, Bi₂S₃ and SnS₂, the total number of black coloured sulphides are:

7

9

8

6

Solution:

The total number of black colored sulfides is 6. These include PbS, CuS, HgS, NiS, CoS, Bi₂S₃. Bi₂S₃ in its crystalline form is dark brown but Bi₂S₃ precipitate obtained is black in color. Hence, the correct option is A