Which is an incorrect statement ?

Options

A. Diamond is unaffected by conc. Acids, but graphite reacts with hot conc. `HNO_(3)` forming mellitic acid `C_(6)(COOH)_(6)`
B. `CO` is toxic because it forms a complex with hemoglobin in the blood
C. `C_(3)O_(2)`, carbon suboxide, is a foul - smelling gas
D. `COCl_(2)` is called tear gas.

Answer

To determine which statement is incorrect, we will analyze each statement one by one:

1. **Statement 1**: "Diamond is unaffected by concentrated acids but graphite reacts with hot concentrated HNO3 forming malytic acid."
- **Analysis**: This statement is correct. Diamond, being a form of carbon with a tetrahedral structure and strong covalent bonds, is indeed unaffected by concentrated acids. Graphite, on the other hand, can react with concentrated nitric acid (HNO3) to form malonic acid (maletic acid is a typo).

2. **Statement 2**: "CO is toxic because it forms a complex with hemoglobin in the blood."
- **Analysis**: This statement is also correct. Carbon monoxide (CO) binds with hemoglobin in the blood, forming carboxyhemoglobin, which inhibits the blood's ability to carry oxygen, making it toxic.

3. **Statement 3**: "C3O2 (carbon suboxide) is a foul-smelling gas."
- **Analysis**: This statement is correct. Carbon suboxide (C3O2) is known to have a foul smell.

4. **Statement 4**: "COCl2 is called tear gas."
- **Analysis**: This statement is incorrect. COCl2 is actually phosgene, which is a toxic gas, not tear gas. Tear gas is typically referred to as CS gas (C10H5ClN2), which is different from phosgene.

**Conclusion**: The incorrect statement is the fourth one, which misidentifies COCl2 as tear gas.