You are given an aqueous solution and are asked to analyze it for the presence (or absence) of Ag + (aq), Ca2 + (aq), and/or Hg2 + (aq) ions. There are no other metal ions in the solution.  You add aqueous hydrochloric acid (HCl) to the solution, and nothing appears to happen.  You add aqueous sulfuric acid (H2SO4) to the solution, and a white precipitate forms.  You remove (via filtration) the white precipitate, and then add aqueous hydrogen sulfide (H2S) to the solution that remains. A black precipitate forms. Based on these observations, which ions are present in the original solution? (a) Ag + (aq), Ca2 + (aq), and Hg2 + (aq) (b) only Ag + (aq) and Hg2 + (aq) (c) only Ca2 + (aq) and Hg2 + (aq) (d) only Ag + (aq) and Ca2 + (aq) (e) only Hg2 + (aq)

Question

Chemistry

Rachael Flores

29 September, 20:55

You are given an aqueous solution and are asked to analyze it for the presence (or absence) of Ag + (aq), Ca2 + (aq), and/or Hg2 + (aq) ions. There are no other metal ions in the solution.  You add aqueous hydrochloric acid (HCl) to the solution, and nothing appears to happen.  You add aqueous sulfuric acid (H2SO4) to the solution, and a white precipitate forms.  You remove (via filtration) the white precipitate, and then add aqueous hydrogen sulfide (H2S) to the solution that remains. A black precipitate forms. Based on these observations, which ions are present in the original solution? (a) Ag + (aq), Ca2 + (aq), and Hg2 + (aq) (b) only Ag + (aq) and Hg2 + (aq) (c) only Ca2 + (aq) and Hg2 + (aq) (d) only Ag + (aq) and Ca2 + (aq) (e) only Hg2 + (aq)

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Gates · Answer 1

(c) only Ca2 + (aq) and Hg2 + (aq)

Explanation:

In the first step, hydrochloric acid (HCl) is added to the solution. In this case the equilibrium that could take place is:

Ag⁺ (aq) + Cl⁻ (aq) ↔ AgCl (s)

But no precipitate was formed, so Ag⁺ (aq) is absent.

By adding H₂SO₄ (aq) the next equilibrium that could take place is:

Ca⁺² (aq) + SO₄⁻² (aq) ↔ CaSO₄ (s)

A white precipitate was formed, so Ca⁺² is present in the solution.

The following could take place after adding H₂S (aq):

Hg²⁺ (aq) + S⁻² ↔ HgS (s)

A black precipitate formed, so Hg⁺² is present as well.