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An aqueous solution of a substance give...

An aqueous solution of a substance gives a white percipitate on treatment with dil ,HCI which dissolves on heating .When `H_(2)S` is passed through the hot acidic solution a black precipitate is obtained .The substances are not :

A

`Hg_(2)^(2+)` salt

B

`Cu^(2+)` salt

C

`Ag^(o+)` salt

D

`Pb^(2+)` salt

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we need to analyze the information given about the substance in question and the reactions that occur with it. ### Step 1: Identify the Reaction with Dilute HCl The problem states that an aqueous solution of a substance gives a white precipitate when treated with dilute HCl. This indicates that the substance likely contains a cation that forms an insoluble salt with chloride ions. **Hint:** Look for cations that form white precipitates with chloride ions. ### Step 2: Determine the Nature of the White Precipitate The white precipitate dissolves upon heating. One common cation that fits this description is lead (Pb²⁺), which forms lead(II) chloride (PbCl₂), a white precipitate that is soluble in hot water. **Hint:** Consider the solubility rules for chlorides and remember that some precipitates can dissolve upon heating. ### Step 3: Analyze the Reaction with H₂S When H₂S is passed through the hot acidic solution, a black precipitate is formed. This suggests that the cation in the solution can react with sulfide ions to form an insoluble sulfide. Lead(II) ions react with H₂S to form lead(II) sulfide (PbS), which is black. **Hint:** Identify cations that form black precipitates with sulfide ions. ### Step 4: Identify the Cations that Fit the Description From the analysis, we can conclude that the substance must contain lead (Pb²⁺) because it meets both criteria: it forms a white precipitate with dilute HCl that dissolves on heating, and it produces a black precipitate with H₂S. **Hint:** List common cations that form white precipitates with HCl and black precipitates with H₂S. ### Step 5: Determine Which Substances Do Not Fit The question asks for substances that do not produce these reactions. Cations like mercury (Hg²⁺), copper (Cu²⁺), and silver (Ag⁺) do not form a black precipitate with H₂S under the same conditions as lead. Therefore, these substances are not the ones we are looking for. **Hint:** Cross-reference the cations that form precipitates with HCl and H₂S to identify those that do not match the observed results. ### Conclusion The substances that do not produce the described reactions are Hg²⁺, Cu²⁺, and Ag⁺. Thus, the answer to the question is: **Answer:** The substances are not Hg²⁺, Cu²⁺, Ag⁺.
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