Which of the following is pseudo alum ?

Explanation

To determine which of the given options is a pseudo alum, we first need to understand the definitions and general formulas for both regular alum and pseudo alum.

### Step-by-Step Solution:

1. **Understand the General Formula of Alum:**
- Regular alum has the general formula:
\[ M_2SO_4 \cdot M'_{2}(SO_4)_{3} \cdot 24H_2O \]
- Here, \(M\) is a univalent cation (e.g., \(Na^+\), \(K^+\), \(NH_4^+\)) and \(M'\) is a trivalent cation (e.g., \(Al^{3+}\)).

2. **Understand the General Formula of Pseudo Alum:**
- Pseudo alum has the general formula:
\[ MSO_4 \cdot M'_{2}(SO_4)_{3} \cdot 24H_2O \]
- In this case, \(M\) is a divalent cation (e.g., \(Co^{2+}\), \(Mn^{2+}\)), and \(M'\) remains a trivalent cation (e.g., \(Al^{3+}\)).

3. **Identify the Cations in the Options:**
- We need to analyze the options provided to see which one fits the pseudo alum formula.
- Look for a compound that has a divalent cation paired with a trivalent cation.

4. **Evaluate the Given Options:**
- If the options include:
- A. Regular alum (e.g., \(KAl(SO_4)_2 \cdot 12H_2O\))
- B. Another regular alum
- C. A compound like \(MnSO_4 \cdot Al_2(SO_4)_3 \cdot 24H_2O\)
- In this case, option C has \(Mn^{2+}\) (a divalent cation) and \(Al^{3+}\) (a trivalent cation).

5. **Conclusion:**
- Therefore, the correct answer is option C, which is the pseudo alum.

### Final Answer:
**C. \(MnSO_4 \cdot Al_2(SO_4)_3 \cdot 24H_2O\)** is the pseudo alum.

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