Which of the following statement is wrong ?

Options

A. `Tl(III)` salt undergo disproportionation.
B. `CO` is used as a reducing agent.
C. `CO_(2)` is a greenhouse gas.
D. `SiO_(2)` is a convalent solid.

Explanation

To determine which statement is wrong, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A**: Thallium (Tl) +3 salt undergoes disproportionation.

- Disproportionation is a reaction where a single substance is simultaneously oxidized and reduced.
- Thallium in the +3 oxidation state can be reduced to thallium in the +1 oxidation state.
- However, thallium cannot be oxidized further since the maximum oxidation state for thallium in the boron family is +3.
- Therefore, thallium +3 cannot undergo disproportionation as it can only be reduced, not oxidized.

**Conclusion for Statement A**: This statement is false.

### Step 2: Analyze Statement B
**Statement B**: Carbon monoxide is used as a reducing agent.

- In carbon monoxide (CO), the oxidation state of carbon is +2.
- CO can be oxidized to carbon dioxide (CO2), where the oxidation state of carbon is +4.
- Since CO can lose electrons (be oxidized) and in the process can reduce other substances, it acts as a reducing agent.

**Conclusion for Statement B**: This statement is true.

### Step 3: Analyze Statement C
**Statement C**: Carbon dioxide is a greenhouse gas.

- Carbon dioxide (CO2) traps heat in the atmosphere, contributing to the greenhouse effect.
- It is well-documented that CO2 is a greenhouse gas as it increases the average temperature of the Earth.

**Conclusion for Statement C**: This statement is true.

### Step 4: Analyze Statement D
**Statement D**: Silica (SiO2) is a covalent solid.

- Silica is composed of silicon and oxygen atoms bonded together by covalent bonds.
- The structure of SiO2 is a network solid, which is characterized by strong covalent bonds throughout the entire structure, making it a solid.

**Conclusion for Statement D**: This statement is true.

### Final Conclusion
After analyzing all the statements:
- Statement A is the only false statement, indicating that it is the wrong statement.

### Answer: The wrong statement is A.

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