In Alum: `K_(2)SO_(4) Al_(2)(SO_(4))_(3). 24 H_(2)O`
Which metal can replace Al

Options

A. Cr
B. Mn
C. In
D. Sc

Explanation

To determine which metal can replace aluminum in the compound alum, we need to analyze the structure and properties of the compound.

### Step-by-Step Solution:

1. **Identify the Composition of Alum**:
The formula for alum is given as \( K_2SO_4 \cdot Al_2(SO_4)_3 \cdot 24H_2O \). This indicates that alum consists of potassium sulfate and aluminum sulfate along with water of hydration.

**Hint**: Look for the metal cation in the structure of the compound.

2. **Understand the Role of Aluminum**:
In this compound, aluminum exists in the form of \( Al^{3+} \) ions. The aluminum ions are trivalent, meaning they have a +3 charge.

**Hint**: Consider the charge of the metal ions that can replace aluminum.

3. **Identify Potential Replacements**:
To find a suitable replacement for aluminum, we need to look for other metals that can also exist in a +3 oxidation state. The options given are:
- Chromium (Cr)
- Manganese (Mn)
- Indium (In)
- Scandium (Sc)

**Hint**: Check the oxidation states of the metals listed in the options.

4. **Evaluate Each Metal**:
- **Chromium**: Can exist as \( Cr^{3+} \) and can replace \( Al^{3+} \) in the structure of alum, forming chrome alum \( K_2SO_4 \cdot Cr_2(SO_4)_3 \cdot 24H_2O \).
- **Manganese**: Typically exists in +2 or +7 oxidation states, but not commonly in +3.
- **Indium**: Primarily exists in +3 oxidation state, but it does not form a common alum.
- **Scandium**: Can exist as \( Sc^{3+} \) but is not commonly used in alums.

**Hint**: Consider which metals are commonly known to form alums.

5. **Conclusion**:
The only metal from the options provided that can effectively replace aluminum in the alum structure is chromium. Thus, the answer is **Chromium**.

### Final Answer:
The metal that can replace aluminum in alum is **Chromium**.