A clear, blue unknown solution tested neutral to indicator paper. There was no reaction when this unknown was tested with either AgNO3(aq), dilute H2SO4, or BaCl2(aq). A black precipitate was formed when the unknown was treated with Na2S(aq), and a pale blue precipitate was formed when the unknown was treated with KOH(aq). Which of the possible unknown for this experiment would give this behavior? Write a balanced equation for the reactions observed with Na2S and KOH.
Which solution will distinguish between a soluble Cl^- salt solution and a soluble SO4^2- salt solution?