Which of the following is//are autoredox reactions?

Options

A. `P_(4)+overset(ө)OHrarrH_(2)PO_(2)^(ө)+PH_(3)`
B. `S_(2)O_(3)^(2-)rarrSO_(4)^(2-)+S`
C. `H_(2)O_(2)rarrH_(2)O+O_(2)`
D. `AgCl+NH_(3)rarr[Ag(NH)_(3)_(2)]Cl`

Explanation

To determine which of the given reactions are autoredox reactions, we need to analyze each reaction to see if the same substance undergoes both oxidation (loss of electrons) and reduction (gain of electrons). Here’s a step-by-step solution:

### Step 1: Understand the Definition of Autoredox Reactions
An autoredox reaction is one in which the same substance is both oxidized and reduced during the reaction. This means that the oxidation state of the substance changes in both directions.

**Hint:** Remember that oxidation involves an increase in oxidation state, while reduction involves a decrease.

### Step 2: Analyze Each Reaction

#### Reaction A
- **Substance P**:
- Oxidation: Changes from 0 to +5 (oxidized).
- Reduction: Changes from 0 to -3 (reduced).

Since substance P undergoes both oxidation and reduction, this is an autoredox reaction.

**Hint:** Check the oxidation states before and after the reaction to confirm both processes.

#### Reaction B
- **Substance Ag**:
- Oxidation: Changes from +2 to +6 (oxidized).
- Reduction: Changes from +2 to 0 (reduced).

Substance Ag also undergoes both oxidation and reduction, making this an autoredox reaction.

**Hint:** Look for changes in oxidation states for the same substance in the reaction.

#### Reaction C
- **Substance O**:
- Oxidation: Changes from -1 to 0 (oxidized).
- Reduction: Changes from -1 to -2 (reduced).

Oxygen undergoes both oxidation and reduction, indicating that this is an autoredox reaction.

**Hint:** Ensure that the same element is involved in both processes to confirm it’s an autoredox reaction.

#### Reaction D
- **Substance Ag**:
- Oxidation state remains +1 in both cases.

Since there is no change in the oxidation state of Ag, this reaction does not qualify as an autoredox reaction.

**Hint:** If the oxidation state does not change, it cannot be an autoredox reaction.

### Step 3: Conclusion
Based on the analysis:
- Reactions A, B, and C are autoredox reactions.
- Reaction D is not an autoredox reaction.

**Final Answer:** The correct autoredox reactions are A, B, and C.