Substance soluble in ammonia is

Options

A. `Al (OH)_3`
B. `Fe(OH)_3`
C. `Cr(OH)_3`
D. `Cu(OH)_2`

Explanation

To determine which substance is soluble in ammonia, we will analyze the given options step by step.

### Step 1: Understanding Ammonia
Ammonia (NH₃) is a weak base and has the ability to form complexes with certain metal ions. It is important to know which substances can react with ammonia to form soluble complexes.

### Step 2: Analyzing Aluminum
Aluminum (Al) has an amphoteric nature, meaning it can react with both acids and bases. However, ammonia is not a strong base, and aluminum does not react with it. Therefore, aluminum is **not soluble** in ammonia.

**Hint:** Remember that amphoteric substances can react with strong acids or bases, but ammonia is a weak base.

### Step 3: Analyzing Iron Hydroxide
Iron hydroxide (Fe(OH)₂ or Fe(OH)₃) is generally insoluble in excess ammonia. Thus, iron hydroxide is **not soluble** in ammonia.

**Hint:** Check the solubility rules for hydroxides; many are insoluble in weak bases like ammonia.

### Step 4: Analyzing Chromium Hydroxide
Chromium hydroxide (Cr(OH)₃) is slightly soluble in ammonia. However, it does not dissolve significantly to be considered soluble. Therefore, chromium hydroxide is also **not a strong candidate** for solubility in ammonia.

**Hint:** Slight solubility does not equate to being soluble in the context of this question.

### Step 5: Analyzing Copper Hydroxide
Copper hydroxide (Cu(OH)₂) is known to form a complex with ammonia. When copper ions (Cu²⁺) react with ammonia, they form a deep blue-colored complex, [Cu(NH₃)₄]²⁺. This indicates that copper hydroxide is indeed **soluble** in ammonia due to the formation of this complex.

**Hint:** Look for color changes or complex formations as indicators of solubility in ammonia.

### Conclusion
From the analysis, the substance that is soluble in ammonia is **Copper Hydroxide**.

**Final Answer:** Copper Hydroxide is soluble in ammonia.