Pick out the correct statement(s):

Options

A. `MnO_(2)` dissolves in conc.HCl but does not form `Mn^(4+)` ions
B. Decomposition of acidic `KMnO_(4)` is not catalyst by sunlight
C. `MnO_(4)^(2-)` is stongly oxidising and stable only in very strong alkali. In dilute alkali, water or acidic solutions it disproportionates
D. `KMnO_(4)` does not act as oxidising agent in alkaline medium

Explanation

To determine the correct statements regarding the properties of manganese compounds, we will analyze each statement step by step.

### Step 1: Analyze Statement A
**Statement A:** "MnO2 dissolves in concentrated HCl, but does not form Mn4+ ions."

- **Reaction:** When MnO2 reacts with concentrated HCl, it forms MnCl2, Cl2, and water.
- **Chemical Equation:**
\[ \text{MnO}_2 + 4 \text{HCl} \rightarrow \text{MnCl}_2 + 2 \text{Cl}_2 + 2 \text{H}_2\text{O} \]
- **Oxidation State:** In MnCl2, manganese is in the +2 oxidation state (Mn2+).
- **Conclusion:** This statement is correct as MnO2 does not form Mn4+ ions in this reaction.

### Step 2: Analyze Statement B
**Statement B:** "Decomposition of acidic KMnO4 is not catalyzed by sunlight."

- **Reaction:** The decomposition of KMnO4 in acidic conditions is indeed catalyzed by sunlight.
- **Chemical Equation:**
\[ 2 \text{KMnO}_4 \rightarrow \text{MnO}_2 + \text{O}_2 + \text{K}_2\text{O} + \text{H}_2\text{O} \]
- **Conclusion:** This statement is incorrect as sunlight does catalyze the decomposition of KMnO4.

### Step 3: Analyze Statement C
**Statement C:** "MnO4- is strongly oxidizing and stable only in very strong alkali; in dilute alkali or acidic solution, it disproportionates."

- **Reaction:** In dilute alkaline conditions, MnO4- can disproportionate.
- **Chemical Equation:**
\[ 3 \text{MnO}_4^- + 2 \text{H}_2\text{O} \rightarrow 2 \text{MnO}_2 + \text{MnO}_4^{2-} + 4 \text{OH}^- \]
- **Conclusion:** This statement is correct as MnO4- is a strong oxidizing agent and disproportionates in dilute conditions.

### Step 4: Analyze Statement D
**Statement D:** "KMnO4 does not act as an oxidizing agent in alkaline medium."

- **Reaction:** KMnO4 does act as an oxidizing agent in alkaline medium.
- **Chemical Equation:**
\[ \text{MnO}_4^- + 2 \text{H}_2 + 3 \text{e}^- \rightarrow \text{MnO}_2 + 4 \text{OH}^- \]
- **Conclusion:** This statement is incorrect as KMnO4 is indeed an oxidizing agent in alkaline medium.

### Final Conclusion
The correct statements are:
- **Statement A:** MnO2 dissolves in concentrated HCl, but does not form Mn4+ ions.
- **Statement C:** MnO4- is strongly oxidizing and stable only in very strong alkali; in dilute alkali or acidic solution, it disproportionates.

### Summary of Correct Statements
- **Correct Statements:** A and C