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An aqueous solution of compound 'A' give...

An aqueous solution of compound `'A'` gives white precipitate with `2M HCl`.The precipitate becomes black on addition of aqueous `NH_(3)` due to formation of `'B'`.`'B'` dissolves in aquaregia. `'A'` and `'B'` are:

A

`Hg^(2+)` and `Hg Cl_(2)`

B

`Hg_(2)^(2+)` and `Hg_(2) Cl_(2)`

C

`Hg^(2+)` and `Hg (NH_(2))Cl+Hg`

D

`Hg_(2)^(2+)` and `Hg (NH_(2))Cl+Hg`

Text Solution

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The correct Answer is:
To solve the problem, we need to identify the compounds 'A' and 'B' based on the given reactions and observations. Here’s a step-by-step breakdown: ### Step 1: Identify Compound 'A' The problem states that an aqueous solution of compound 'A' gives a white precipitate when treated with 2M HCl. - When we add 2M HCl to a solution containing mercury(I) ions (Hg₂²⁺), it forms mercurous chloride (Hg₂Cl₂), which is known as calomel. This compound is white in color. **Conclusion:** Compound 'A' is Hg₂²⁺ (mercury(I) ion). ### Step 2: Formation of Precipitate The white precipitate formed is Hg₂Cl₂ (calomel). ### Step 3: Reaction with Aqueous NH₃ Next, we add aqueous NH₃ to the white precipitate (Hg₂Cl₂). - The reaction of Hg₂Cl₂ with NH₃ produces elemental mercury (Hg) and a complex, which is Hg(NH₂)Cl. The elemental mercury is black in color, and the presence of this black precipitate indicates that 'B' is formed. **Conclusion:** The precipitate becomes black due to the formation of elemental mercury (Hg). ### Step 4: Identify Compound 'B' The problem states that 'B' dissolves in aqua regia. - Aqua regia is a mixture of hydrochloric acid and nitric acid, which can dissolve noble metals including mercury. Therefore, 'B' must be elemental mercury (Hg), which can dissolve in aqua regia. **Conclusion:** Compound 'B' is Hg (elemental mercury). ### Final Answer - Compound 'A' is Hg₂Cl₂ (calomel). - Compound 'B' is Hg (elemental mercury). ### Summary - A = Hg₂Cl₂ (calomel) - B = Hg (elemental mercury) ---
To solve the problem, we need to identify the compounds 'A' and 'B' based on the given reactions and observations. Here’s a step-by-step breakdown: ### Step 1: Identify Compound 'A' The problem states that an aqueous solution of compound 'A' gives a white precipitate when treated with 2M HCl. - When we add 2M HCl to a solution containing mercury(I) ions (Hg₂²⁺), it forms mercurous chloride (Hg₂Cl₂), which is known as calomel. This compound is white in color. **Conclusion:** Compound 'A' is Hg₂²⁺ (mercury(I) ion). ...
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