`AgNO_(3)`given white ppt with hypo changing to black after some time .Black ppt is of

Options

A. `Ag_(2)S_(2)O_(3)`
B. `Ag_(2)SO_(4)`
C. `Ag_(2)S_(4)O_(6)`
D. `Ag_(2)S`

Answer

To solve the problem step by step, we need to analyze the reaction between silver nitrate (AgNO₃) and sodium thiosulphate (hypo).

### Step 1: Identify the Reactants
The given reactants are:
- Silver nitrate (AgNO₃)
- Sodium thiosulphate (Na₂S₂O₃), commonly known as hypo.

### Step 2: Understand the Reaction
When silver nitrate reacts with sodium thiosulphate, a precipitation reaction occurs. The initial product formed is silver thiosulphate (Ag₂S₂O₃), which is a white precipitate.

### Step 3: Write the Reaction Equation
The balanced chemical equation for the reaction can be written as:
\[ 2 \text{AgNO}_3 + \text{Na}_2\text{S}_2\text{O}_3 \rightarrow \text{Ag}_2\text{S}_2\text{O}_3 \downarrow + 2 \text{NaNO}_3 \]
Here, Ag₂S₂O₃ is the white precipitate that forms.

### Step 4: Identify the Change Over Time
The white precipitate of silver thiosulphate (Ag₂S₂O₃) further reacts with water over time. This reaction leads to the formation of silver sulfide (Ag₂S), which is a black precipitate.

### Step 5: Write the Reaction for the Formation of Black Precipitate
The reaction that leads to the formation of the black precipitate can be represented as:
\[ \text{Ag}_2\text{S}_2\text{O}_3 + \text{H}_2\text{O} \rightarrow \text{Ag}_2\text{S} \downarrow + \text{H}_2\text{SO}_4 \]
Here, Ag₂S is the black precipitate formed.

### Step 6: Conclusion
Thus, the black precipitate formed after some time is silver sulfide (Ag₂S).

### Final Answer
The black precipitate is Ag₂S.

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