Question

A solution may contain one or more of the Group I cations. A white precipitate forms when 6 M HCl is added to the solution. The precipitate is insoluble in hot water. The precipitate is then found to be completely soluble in 6M NH4OH. Indicate whether each of the following cations is present, undetermined, or absent.

• Pb²⁺
• Ag+
• HG₂²⁺

Answer 1

The white precipitate formed when 6 M HCl is added to the solution indicates the presence of certain cations, which can be determined by their solubility in hot water and NH4OH. Based on this, we can determine if Pb²⁺, Ag⁺, and Hg₂²⁺ are present.

Step-by-step explanation:

The white precipitate formed when 6 M HCl is added to the solution indicates the presence of certain cations. The precipitate is insoluble in hot water, but it is completely soluble in 6 M NH4OH. Based on this information, we can determine which cations are present.

Pb²⁺: PbCl₂ is soluble in hot water, so if the precipitate dissolves in hot water, Pb²⁺ is present.

Ag⁺: AgCl is insoluble in water, but it dissolves in NH4OH. If the precipitate dissolves in NH4OH, then Ag⁺ is present.

Hg₂²⁺: Hg₂Cl₂ is also insoluble in water and dissolves in NH4OH. If the precipitate dissolves in NH4OH, Hg₂²⁺ is present.