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To a solution of a substance, gradual ad...

To a solution of a substance, gradual addition of ammonium hydroxide results in a brownish black precipitate which does not dissolve in excess of `NH_(4)OH`.However, when `Kl` (not in excess) is added to the original solution, a green precipitate is formed. The solution contained :

A

Lead salt

B

Silver salt

C

Mercurous salt

D

Copper salt.

Text Solution

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The correct Answer is:
To solve the problem step by step, we need to analyze the information provided in the question and the reactions involved with the substances mentioned. ### Step 1: Identify the precipitate formed with ammonium hydroxide (NH₄OH) - The question states that the gradual addition of ammonium hydroxide results in a brownish-black precipitate that does not dissolve in excess NH₄OH. - This indicates that the substance likely contains silver ions (Ag⁺), which can form silver oxide (Ag₂O), a brownish-black precipitate. **Hint:** Look for substances that form a precipitate with ammonium hydroxide and check the color of the precipitate. ### Step 2: Analyze the second reaction with potassium iodide (KI) - The question also mentions that when KI is added to the original solution (not in excess), a green precipitate is formed. - The formation of a green precipitate suggests the presence of a mercurous ion (Hg₂²⁺), which can react with iodide ions (I⁻) to form mercurous iodide (Hg₂I₂), which is green. **Hint:** Consider the reactions of iodide ions with potential cations in the solution to determine the color of the precipitate formed. ### Step 3: Evaluate the possible substances - **Lead salts (Pb²⁺)**: Would form a white precipitate with NH₄OH, which does not match the brownish-black precipitate described. - **Silver salts (Ag⁺)**: Would form a brownish-black precipitate with NH₄OH, but would not typically form a green precipitate with KI. - **Mercurous salts (Hg₂²⁺)**: Would form a black precipitate with NH₄OH and a green precipitate with KI, matching both conditions stated in the question. - **Copper salts (Cu²⁺)**: Would form a blue precipitate with NH₄OH, which does not match the description. **Hint:** Eliminate options based on the color of the precipitates formed with the reagents used. ### Step 4: Conclusion - Based on the analysis, the only substance that fits both criteria (black precipitate with NH₄OH and green precipitate with KI) is mercurous salt (Hg₂²⁺). **Final Answer:** The solution contained mercurous salt.
To solve the problem step by step, we need to analyze the information provided in the question and the reactions involved with the substances mentioned. ### Step 1: Identify the precipitate formed with ammonium hydroxide (NH₄OH) - The question states that the gradual addition of ammonium hydroxide results in a brownish-black precipitate that does not dissolve in excess NH₄OH. - This indicates that the substance likely contains silver ions (Ag⁺), which can form silver oxide (Ag₂O), a brownish-black precipitate. **Hint:** Look for substances that form a precipitate with ammonium hydroxide and check the color of the precipitate. ...
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