A white, sublimable inorganic substance gives a brown precipitate on treatment with nessler's reagent and a whiite precipitate (soluble in `NH_(3)`) with ann `AgNO_(3)` solution. The substance is :

Options

A. `Hg_(2)Cl_(2)`
B. `HgCl_(2)`
C. `As_(2)O_(3)`
D. `NH_(4)Cl`

Answer

To solve the problem step by step, we need to analyze the information given about the white sublimable inorganic substance and the reactions it undergoes.

### Step 1: Identify the Reactions
The substance gives two key reactions:
1. A brown precipitate with Nessler's reagent.
2. A white precipitate that is soluble in ammonia when treated with AgNO3.

### Step 2: Understand Nessler's Reagent
Nessler's reagent is K2HgI4 in KOH, which is used to detect ammonia (NH3) or ammonium ions (NH4+). When NH3 or NH4+ is present, it forms a brown precipitate known as the iodide of melon's base (Hg2I2·NH2).

### Step 3: Analyze the Brown Precipitate
The formation of a brown precipitate indicates the presence of ammonium ions (NH4+). This suggests that the white sublimable inorganic substance is likely to contain ammonium ions.

### Step 4: Examine the White Precipitate with AgNO3
When the substance reacts with AgNO3, it forms a white precipitate. The reaction can be represented as:
\[ \text{NH}_4\text{Cl} + \text{AgNO}_3 \rightarrow \text{AgCl} \downarrow + \text{NH}_4\text{NO}_3 \]
Here, AgCl is the white precipitate formed.

### Step 5: Solubility of the White Precipitate in Ammonia
The white precipitate (AgCl) is soluble in ammonia, forming a colorless complex:
\[ \text{AgCl} + 2\text{NH}_3 \rightarrow \text{[Ag(NH}_3\text{)}_2]^+ + \text{Cl}^- \]
This confirms that the white precipitate is indeed AgCl, which is consistent with the presence of ammonium ions.

### Step 6: Conclusion
Based on the reactions and the analysis, the white sublimable inorganic substance that gives a brown precipitate with Nessler's reagent and a white precipitate soluble in ammonia is **ammonium chloride (NH4Cl)**.

### Final Answer
The substance is **NH4Cl** (ammonium chloride).

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