Consider three P, Q, R, salts among them P and Q salts have different cations annd also have different coloured polyatomic anion due to charge transfer phenomenon while P and R salts have same cation but have different anions. Salts R decomposes into an acidic gas an a basic gas.
Q. If salt Q underrgoes redox reaction with `H_(2)S` in acidic medium then which of the following speies can not be possible product?

Options

A. `MnO_(4)^(2-)(aq.)`
B. `S`
C. `MnO_(2)`
D. Both (a) and (c)

Explanation

To solve the question, we need to analyze the redox reaction between salt Q and H₂S in an acidic medium. Here’s a step-by-step breakdown of the solution:

### Step 1: Identify the nature of salt Q
- Salt Q contains a different cation and a colored polyatomic anion. Given the context of the problem, we can assume that the polyatomic anion is likely to be MnO₄⁻ (permanganate), which is known for its strong oxidizing properties.

**Hint:** Look for common colored polyatomic anions that can act as oxidizing agents.

### Step 2: Determine the role of H₂S
- In the reaction, H₂S acts as a reducing agent. This means that it will donate electrons and reduce the oxidizing agent (in this case, MnO₄⁻).

**Hint:** Remember that reducing agents are substances that lose electrons during a chemical reaction.

### Step 3: Predict the products of the reaction
- The reaction between MnO₄⁻ and H₂S in acidic medium typically produces manganese ions (Mn²⁺) and elemental sulfur (S). The half-reaction for the reduction of MnO₄⁻ can be represented as:
\[ \text{MnO}_4^- + 8\text{H}^+ + 5\text{e}^- \rightarrow \text{Mn}^{2+} + 4\text{H}_2\text{O} \]
- H₂S gets oxidized to sulfur (S):
\[ \text{H}_2\text{S} \rightarrow \text{S} + 2\text{H}^+ + 2\text{e}^- \]

**Hint:** Consider the oxidation states of the elements involved to identify the products formed.

### Step 4: Analyze the possible products
- The question asks which species cannot be a possible product of the reaction. The potential products from the reaction are:
- Mn²⁺ (from MnO₄⁻)
- S (from H₂S)
- MnO₂ (which has Mn in the +4 oxidation state)
- MnO₄²⁻ (which is a reduced form of MnO₄⁻)

### Step 5: Determine which species cannot be produced
- From the reaction, we can conclude:
- Mn²⁺ and S are indeed produced.
- MnO₂ cannot be produced because it requires a different oxidation state for manganese that is not achieved in this reaction.
- MnO₄²⁻ is also not produced because the reaction does not yield this species under acidic conditions.

**Final Conclusion:** The species that cannot be possible products are MnO₂ and MnO₄²⁻.

### Final Answer:
The correct answer is option 4: both A (MnO₄²⁻) and C (MnO₂) cannot be possible products.

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