Question

Select reaction in which precipitate is formed?

• A. Ag$^+$ + SO$_{3(excess)}^{-2}$ $\longrightarrow$
• B. Ba$_{(aq.)}^{+2}$ + S$_2$O$_3^{-2}$ $\longrightarrow$
• C. Cu$_{(aq.)}^{+2}$ + S$_2$O$_3^{-2}$ $\longrightarrow$
• D. Hg$_{(aq.)}^{+2}$ + S$^{-2}$ $\longrightarrow$

Answer 1

Answer: (D)

Hg$_{(aq.)}^{+2}$ + S$^{-2}$ $\longrightarrow$

Answer 2

Mercury(II) ions (Hg$^{2+}$) react with sulfide ions (S$^{2-}$) to form mercury(II) sulfide (HgS). Mercury(II) sulfide is extremely insoluble in water and is a black precipitate.

Hg$^{2+}$ + S$^{2-}$ $\longrightarrow$ HgS(s)