Select the correct statement :

Options

A. `PH_3` 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.

Explanation

To solve the question, we need to evaluate each statement provided and determine if they are correct. Let's analyze each statement step by step.

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

- **Analysis:** At pH 3, phosphine (PH3) can act as a reducing agent. When it reacts with silver nitrate (AgNO3) in the presence of water, it produces metallic silver (Ag), nitric acid (HNO3), and phosphorous acid (H3PO3). The balanced equation for this reaction can be represented as:

\[ 6 \text{PH}_3 + 6 \text{AgNO}_3 + 6 \text{H}_2\text{O} \rightarrow 6 \text{Ag} + 6 \text{HNO}_3 + 6 \text{H}_3\text{PO}_3 \]

- **Conclusion:** The first statement is correct.

### Step 2: Evaluate the second statement
**Statement 2:** Organic tissues turn AgNO3 black by reducing it to Ag.

- **Analysis:** Organic tissues can indeed reduce silver nitrate (AgNO3) to metallic silver (Ag). This reduction typically results in the formation of finely divided silver, which appears black. This is a common reaction observed in photographic processes and other applications.

- **Conclusion:** The second statement is also correct.

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

- **Analysis:** Silver cyanide (AgCN) can react with potassium cyanide (KCN) to form a soluble complex known as potassium argentocyanide, represented as K[Ag(CN)2]. This complex formation indicates that AgCN is indeed soluble in KCN.

- **Conclusion:** The third statement is correct.

### Final Conclusion
Since all three statements have been evaluated and found to be correct, we conclude that the correct answer is:

**All statements are correct.**