The most common trivalent cations forming alum is/are

Options

A. `Fe^(3+)`
B. `Cr^(3+)`
C. `AI^(3+)`
D. `Ce^(3+)`

Answer

To determine the most common trivalent cations forming alum, we can follow these steps:

### Step 1: Understand what alum is
Alum is a type of double sulfate salt that typically contains a trivalent cation and a univalent cation. The general formula for alums can be represented as M2(SO4)3·nH2O, where M is a univalent cation (like potassium or sodium) and the trivalent cation can be aluminum, chromium, iron, or others.

**Hint:** Recall the general formula for alums and the types of cations involved.

### Step 2: Identify common trivalent cations
The most common trivalent cations that can form alums include:
- Aluminum (Al³⁺)
- Chromium (Cr³⁺)
- Iron (Fe³⁺)
- Other cations like Cerium (Ce³⁺) can also form alums, but they are less common.

**Hint:** List the trivalent cations and check their prevalence in alum formation.

### Step 3: Analyze the given options
The question provides four options for trivalent cations:
1. Fe³⁺
2. Cr³⁺
3. Al³⁺
4. Ce³⁺

From our knowledge, all these cations can form alums, but we need to identify which one is the most common.

**Hint:** Consider the frequency of use in industrial and laboratory settings for each cation.

### Step 4: Determine the most common trivalent cation
Among the listed cations, Aluminum (Al³⁺) is the most common trivalent cation used in the formation of alums. Potassium alum, for example, is one of the most widely used forms of alum, which prominently features aluminum.

**Hint:** Think about which alum is most frequently encountered in practical applications.

### Conclusion
The most common trivalent cation forming alum is Aluminum (Al³⁺).

**Final Answer:** Aluminum (Al³⁺) is the most common trivalent cation forming alum.

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