Select the correct statement :

Options

A. `PH_(3)` is reduces `AgNO_(3)` to metallic Ag.
B. Organic tissues turn `AgNO_(3)` black by reducing it to Ag.
C. `AgCN` is soluble in KCN.
D. All are correct statements.

Answer

To solve the question, we need to evaluate each of the statements provided and determine their correctness. Let's analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** pH 3 reduces AgNO3 to metallic Ag.

**Analysis:**
- At pH 3, the medium is acidic. In acidic conditions, certain substances can reduce silver nitrate (AgNO3) to metallic silver (Ag).
- The reaction can be represented as:
\[ 6 \text{AgNO}_3 + \text{H}_3\text{PO}_3 \rightarrow 6 \text{Ag} + 3 \text{HNO}_3 \]
- This indicates that AgNO3 is indeed reduced to metallic Ag.

**Conclusion:** This statement is **correct**.

### Step 2: Analyze the second statement
**Statement:** Organic tissue turns AgNO3 black by reducing it to Ag.

**Analysis:**
- Organic tissues, when they come in contact with silver nitrate, can reduce it to metallic silver, which appears as a black stain.
- The reaction can be summarized as:
\[ \text{AgNO}_3 \rightarrow \text{Ag (black solid)} + \text{other products} \]
- The formation of finely divided silver results in a black coloration.

**Conclusion:** This statement is **correct**.

### Step 3: Analyze the third statement
**Statement:** AgCN is soluble in KCN.

**Analysis:**
- Silver cyanide (AgCN) can react with potassium cyanide (KCN) to form a soluble complex.
- The reaction can be represented as:
\[ \text{AgCN} + 2 \text{KCN} \rightarrow \text{K}_2\text{Ag(CN)}_2 \]
- The resulting complex, potassium dicyanoargentate, is soluble in water.

**Conclusion:** This statement is **correct**.

### Step 4: Evaluate the overall correctness of the statements
Since all three statements have been analyzed and found to be correct, we conclude that:

**Final Answer:** All statements are correct.