Which of the following combination of species undergo(es) comproportionation?

Options

A. `MnO_(4)^(-)(aq.)+Mn^(2+)(aq.)overset(ZnO//ZnSO_(4))to`
B. `S+conc.underset((excess))(H_(2)SO_(4)) overset(warm)to`
C. `PH_(3)+H_(3)PO_(4) to`
D. `NO(g)+NO_(2)(g) overset("cool")to`

Answer

To determine which of the given combinations of species undergo comproportionation, we need to analyze each reaction and identify the changes in oxidation states of the elements involved. Comproportionation occurs when two different oxidation states of the same element react to form a product with an intermediate oxidation state.

### Step-by-Step Solution:

1. **Analyze Reaction A: MnO4- + Mn2+ → MnO2 + H+**
- In MnO4-, manganese is in the +7 oxidation state.
- In Mn2+, manganese is in the +2 oxidation state.
- In MnO2, manganese is in the +4 oxidation state.
- Here, manganese from two different oxidation states (+7 and +2) combines to form manganese in an intermediate oxidation state (+4).
- **Conclusion**: This is a comproportionation reaction.

2. **Analyze Reaction B: S + H2SO4 → SO2 + H2O**
- In elemental sulfur (S), the oxidation state is 0.
- In H2SO4, sulfur is in the +6 oxidation state.
- In SO2, sulfur is in the +4 oxidation state.
- Here, sulfur from two different oxidation states (0 and +6) combines to form sulfur in an intermediate oxidation state (+4).
- **Conclusion**: This is also a comproportionation reaction.

3. **Analyze Reaction C: pH3 + H3PO4 → No Reaction**
- Since there is no reaction, we cannot analyze oxidation states here.
- **Conclusion**: This does not undergo comproportionation.

4. **Analyze Reaction D: NO + NO2 → N2O + O2**
- In NO, nitrogen is in the +2 oxidation state.
- In NO2, nitrogen is in the +4 oxidation state.
- In N2O, nitrogen is in the +1 oxidation state, and O2 has an oxidation state of 0.
- Although there are changes in oxidation states, nitrogen does not combine from different oxidation states to form a product with an intermediate oxidation state. Thus, this is not a comproportionation reaction.
- **Conclusion**: This does not undergo comproportionation.

### Final Answer:
The combinations that undergo comproportionation are:
- **A (MnO4- + Mn2+)**
- **B (S + H2SO4)**