Which of the following compound undergoes disproportionation in presence of `SO_(3)` gas?

Options

A. `K_(2)MnO_(4)`
B. `K_(2)CrO_(4)`
C. `I_(2)`
D. `Mg(NO_(3))_(2)`

Explanation

To determine which compound undergoes disproportionation in the presence of SO₃ gas, we will analyze the given options step by step.

### Step 1: Understand Disproportionation Reaction
A disproportionation reaction is a type of redox reaction where a single substance is both oxidized and reduced, resulting in two different products. This means that one part of the substance increases in oxidation state (oxidation) while another part decreases in oxidation state (reduction).

**Hint:** Remember that in disproportionation, the same element in the same compound changes its oxidation state in two different directions.

### Step 2: Analyze the Compounds
We have the following compounds to consider:
1. K₂MnO₄
2. K₂CrO₄
3. I₂ (iodine gas)
4. Mg(NO₃)₂ (magnesium nitrate)

### Step 3: Examine K₂MnO₄
- K₂MnO₄ contains manganese in the +6 oxidation state.
- When K₂MnO₄ is treated with SO₃, it can undergo disproportionation.
- The manganese can be oxidized to KMnO₄ (where manganese is +7) and reduced to MnO₂ (where manganese is +4).

**Hint:** Look for changes in oxidation states of manganese in K₂MnO₄ when reacting with SO₃.

### Step 4: Examine K₂CrO₄
- K₂CrO₄ contains chromium in the +6 oxidation state.
- While it can undergo redox reactions, it does not typically undergo disproportionation in the presence of SO₃.

**Hint:** Consider whether chromium can change its oxidation state in a similar way as manganese.

### Step 5: Examine I₂
- I₂ (iodine gas) can undergo disproportionation in some reactions, but not specifically in the presence of SO₃.

**Hint:** Think about whether iodine can be oxidized and reduced simultaneously.

### Step 6: Examine Mg(NO₃)₂
- Magnesium nitrate does not have any elements that can undergo disproportionation in the presence of SO₃.

**Hint:** Check if magnesium or nitrate can change oxidation states in a disproportionation reaction.

### Step 7: Conclusion
After analyzing all options, we find that K₂MnO₄ is the only compound that undergoes disproportionation in the presence of SO₃ gas, producing KMnO₄ and MnO₂.

**Final Answer:** K₂MnO₄ undergoes disproportionation in the presence of SO₃ gas.