Which of the following is not a disproportionation reaction :-

Options

A. `P_(4)+NaOHtoNaH_(2)PO_(2)+PH_(3)`
B. `BaC_(2)+N_(2)toBa(CN)_(2)`
C. `Hg_(2)l_(2)toHgl_(2)+Hg`
D. `Cl_(2(g))+2OH_(("aq"))^(-)toClO_(("aq"))^(-)+Cl_(("aq))^(-)+H_(2)O`

Answer

To determine which of the following reactions is not a disproportionation reaction, we need to understand the concept of disproportionation. A disproportionation reaction is one in which a single substance is both oxidized and reduced, resulting in two different products containing the same element in different oxidation states.

Let's analyze the given options step by step:

### Step 1: Identify the reactions
Assume we have the following reactions (for the sake of example):
1. \( P_4 + NaOH \rightarrow NaH_2PO_2 + PH_3 \)
2. \( BaC_2 + N_2 \rightarrow BaCN \)

### Step 2: Analyze the first reaction
**Reaction 1: \( P_4 + NaOH \rightarrow NaH_2PO_2 + PH_3 \)**

- **Oxidation State of Phosphorus in \( P_4 \)**:
- In its elemental form \( P_4 \), the oxidation state of phosphorus is 0.

- **Oxidation State in Products**:
- In \( NaH_2PO_2 \):
- Sodium (Na) = +1, Hydrogen (H) = +1 (2 H = +2), Oxygen (O) = -2 (2 O = -4)
- Let the oxidation state of phosphorus be \( x \):
\[ x + 1 + 2 - 4 = 0 \implies x = +1 \]
- In \( PH_3 \):
- Let the oxidation state of phosphorus be \( y \):
\[ y + 3 = 0 \implies y = -3 \]

- **Conclusion for Reaction 1**:
- Phosphorus goes from 0 (in \( P_4 \)) to +1 (in \( NaH_2PO_2 \)) - this is oxidation.
- Phosphorus goes from 0 (in \( P_4 \)) to -3 (in \( PH_3 \)) - this is reduction.
- Therefore, this reaction is a disproportionation reaction.

### Step 3: Analyze the second reaction
**Reaction 2: \( BaC_2 + N_2 \rightarrow BaCN \)**

- **Oxidation State of Barium**:
- In \( BaC_2 \), barium (Ba) is +2.
- In \( BaCN \), barium (Ba) remains +2.

- **Oxidation State of Carbon**:
- In \( BaC_2 \), if we assume carbon is -1 (for two carbons, total -2), then barium is +2, making the compound neutral.
- In \( BaCN \), carbon is +4 (in cyanide).

- **Conclusion for Reaction 2**:
- There is no change in the oxidation state of barium, and the carbon is not being oxidized and reduced in the same reaction.
- Therefore, this reaction does not involve both oxidation and reduction of the same species, and hence it is not a disproportionation reaction.

### Final Conclusion
The reaction that is **not** a disproportionation reaction is **Reaction 2**: \( BaC_2 + N_2 \rightarrow BaCN \).