`Al^(3+).Fe^3+. Cr^3+` are grouped together for qualitative analysis because their

Options

A. carbonates are insoluble in ammonia
B. hydroxides are insoluble in ammonia
C. sulphides are soluble in acids
D. electronic charge is the same

Answer

To solve the question regarding why Al^(3+), Fe^(3+), and Cr^(3+) are grouped together for qualitative analysis, we can follow these steps:

### Step 1: Identify the Ions
We are given three ions: Al^(3+), Fe^(3+), and Cr^(3+).

### Step 2: Understand the Grouping in Qualitative Analysis
In qualitative analysis, ions are often grouped based on their chemical properties, particularly their solubility or insolubility in certain reagents.

### Step 3: Analyze the Hydroxides
Al^(3+), Fe^(3+), and Cr^(3+) form hydroxides when reacted with hydroxide ions (OH^-). The hydroxides of these metals (Al(OH)₃, Fe(OH)₃, and Cr(OH)₃) are known to be insoluble in water.

### Step 4: Consider the Role of Ammonia
In qualitative analysis, ammonia (NH₃) can be used to precipitate hydroxides. The hydroxides of Al^(3+), Fe^(3+), and Cr^(3+) do not dissolve in ammonia, which is a key characteristic that allows them to be grouped together.

### Step 5: Conclusion
Thus, Al^(3+), Fe^(3+), and Cr^(3+) are grouped together in qualitative analysis because their hydroxides are insoluble in ammonia, allowing for their identification through precipitation reactions.

### Final Answer
The correct reason for grouping Al^(3+), Fe^(3+), and Cr^(3+) together in qualitative analysis is that their hydroxides are insoluble in ammonia.