Which of the following is an intermolecular redox reaction?

Options

A. `2OCH-CHOoverset(overset(ө)OH)rarrHOCH_(2)-CH_(2)OH`
B. `2C_(6)H_(5)CHOoverset(Al(OC_(2)H_(5))_(3))rarrC_(6)H_(5)COOH+C_(6)H_(5)CH_(2)OH`
C. `4CrO_(5)+6H_(2)SO_(4)rarr2Cr_(2)(SO)_(4))_(3)+6H_(2)O+7O_(2)`
D. `As_(2)S_(3)+HNO_(3)rarrH_(3)AsO_(4)rarrH_(3)AsO_(4)+H_(2)SO_(4)+NO`

Explanation

To determine which of the given options represents an intermolecular redox reaction, we need to follow these steps:

### Step 1: Understand Intermolecular Redox Reactions
An intermolecular redox reaction involves two different molecules where one molecule undergoes oxidation (loss of electrons) and the other undergoes reduction (gain of electrons).

### Step 2: Analyze Each Option
We will analyze each option provided to identify if they involve two different molecules undergoing oxidation and reduction.

1. **Option 1**: Contains only one type of reactant molecule.
- This cannot be an intermolecular redox reaction because it involves only one molecule that cannot simultaneously undergo oxidation and reduction.

2. **Option 2**: Again, involves only one type of reactant molecule.
- Similar to option 1, this cannot be an intermolecular redox reaction for the same reason.

3. **Option 3**: Involves two reactant species.
- We need to determine the oxidation states of the elements involved.
- For example, in CrO5, chromium is in the +6 oxidation state, and in H2SO4, sulfur is in the +6 oxidation state.
- If one species is reduced (oxidation state decreases) and the other is oxidized (oxidation state increases), then this can be an intermolecular redox reaction. However, if only one molecule is changing oxidation states, it cannot be classified as intermolecular.

4. **Option 4**: Involves two different reactant species (e.g., HNO3 and AS2S3).
- Here, we can calculate the oxidation states:
- In HNO3, nitrogen is in the +5 oxidation state, which reduces to +2 in NO.
- In AS2S3, arsenic is in the +3 oxidation state and oxidizes to +5 in H3AsO4.
- Since one species is undergoing oxidation and the other is undergoing reduction, this qualifies as an intermolecular redox reaction.

### Step 3: Conclusion
After analyzing all options, **Option 4** is the correct answer as it involves two different molecules where one undergoes oxidation and the other undergoes reduction.

### Final Answer
**Option 4** is an intermolecular redox reaction.

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