On adding ammonia hydroxide solution to a solution of a salt, a dirty green precipitate appears. This precipitate, however, remains insoluble on addition of an excess of ammonia solution. Which metal solution is present ?

Options

A. Na
B. Zn
C. Fe
D. Al

Explanation

To determine the metal present in the solution based on the given information, we can follow these steps:

### Step 1: Identify the Reaction
When ammonia hydroxide (NH4OH) is added to a solution of a salt, a precipitate forms. The question states that a dirty green precipitate appears, which suggests the formation of a metal hydroxide.

**Hint:** Look for common metal hydroxides that form precipitates with ammonia.

### Step 2: Analyze the Color of the Precipitate
The color of the precipitate is described as "dirty green." This is characteristic of ferrous hydroxide (Fe(OH)2), which is known to have a greenish color.

**Hint:** Recall the colors of precipitates formed by different metal hydroxides to narrow down the possibilities.

### Step 3: Consider the Solubility in Excess Ammonia
The problem states that the dirty green precipitate remains insoluble even when excess ammonia solution is added. This is a key point because many metal hydroxides can dissolve in excess ammonia, but ferrous hydroxide does not.

**Hint:** Think about which metal hydroxides are known to be insoluble in excess ammonia.

### Step 4: Conclude the Identity of the Metal
Based on the information gathered, the metal that forms a dirty green precipitate with ammonia hydroxide and remains insoluble in excess ammonia is iron (specifically in the +2 oxidation state, Fe²⁺).

**Final Conclusion:** The metal solution present is iron (Fe²⁺).

### Summary of Steps:
1. Identify the reaction with ammonia hydroxide.
2. Analyze the color of the precipitate (dirty green).
3. Consider the solubility of the precipitate in excess ammonia.
4. Conclude that the metal present is iron (Fe²⁺).