A few redox reactions are given as follows:
I. `Cu + 2AgNO_(3) to Cu(NO_(3))_(2) + 2Ag`
II. `3MnO_(2) + 4AI to 3Mn + 2Al_(2)O_(3)`
III. `2HI + Cl_(2) to 2HCl + I_(2)`
IV. `Fe_(2)O_(3) + 3CO to 2Fe + 3CO_(2)`
Select the correct option.

Options

A. In reaction I, copper is an oxidising agent.
B. In reaction II, `MnO_(2)` is oxidised
C. In reaction III, HI is the reducing agent.
D. In reaction IV, `CO_(2)` is reduced.

Answer

To determine the correctness of the statements regarding the given redox reactions, we will analyze each reaction step by step.

### Step 1: Analyze Reaction I
**Reaction:** `Cu + 2AgNO3 → Cu(NO3)2 + 2Ag`

- **Oxidation States:**
- Cu: 0 (elemental state) → +2 (in Cu(NO3)2)
- Ag: +1 (in AgNO3) → 0 (elemental state)

- **Conclusion:**
- Copper (Cu) is oxidized (loses electrons) from 0 to +2.
- Silver (Ag) is reduced (gains electrons) from +1 to 0.
- Therefore, Cu is not an oxidizing agent; it is a reducing agent.

**Verdict:** False.

### Step 2: Analyze Reaction II
**Reaction:** `3MnO2 + 4Al → 3Mn + 2Al2O3`

- **Oxidation States:**
- Mn in MnO2: +4 → 0 (elemental state)
- Al: 0 (elemental state) → +3 (in Al2O3)

- **Conclusion:**
- Manganese (Mn) is reduced from +4 to 0.
- Aluminum (Al) is oxidized from 0 to +3.
- Therefore, MnO2 acts as an oxidizing agent.

**Verdict:** False.

### Step 3: Analyze Reaction III
**Reaction:** `2HI + Cl2 → 2HCl + I2`

- **Oxidation States:**
- H in HI: +1 → +1 (in HCl)
- I in HI: -1 → 0 (elemental state)
- Cl in Cl2: 0 → -1 (in HCl)

- **Conclusion:**
- Iodine (I) is oxidized from -1 to 0.
- Chlorine (Cl) is reduced from 0 to -1.
- Therefore, HI acts as a reducing agent.

**Verdict:** True.

### Step 4: Analyze Reaction IV
**Reaction:** `Fe2O3 + 3CO → 2Fe + 3CO2`

- **Oxidation States:**
- Fe in Fe2O3: +3 → 0 (elemental state)
- C in CO: +2 → +4 (in CO2)

- **Conclusion:**
- Iron (Fe) is reduced from +3 to 0.
- Carbon (C) is oxidized from +2 to +4.
- Therefore, Fe2O3 acts as an oxidizing agent.

**Verdict:** False.

### Final Summary
- Reaction I: False
- Reaction II: False
- Reaction III: True
- Reaction IV: False

### Correct Option
The correct option is that only **Reaction III** is true.